spirit level
Enable an AI agent to recognise a spirit level, assess whether its indications are trustworthy and decide how it may be used to check orientation relative to gravity.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise a spirit level, assess whether its indications are trustworthy and decide how it may be used to check orientation relative to gravity.
A spirit level is a gravity-referenced indicating instrument that shows whether a surface or edge is horizontal or vertical by the displacement of a trapped gas bubble inside a sealed, slightly barrel-shaped liquid-filled vial, whose inner curvature converts a small tilt into a visible bubble movement against scribed marks.
It can be Select a supported vial and reference surface for a horizontal, vertical or incline check.; Place, suspend or attach the level using the method supported by its design.; Observe and record bubble position after establishing stable contact and allowing the indication to settle.; Compare indications after a suitable reversal to investigate consistency.; Clean accessible reference surfaces and inspect vials and mounts before reassessing usability.; Withhold the level from tolerance-critical use when damage, discrepancies or missing accuracy evidence prevent a justified decision..
Distinguishing features
Look for a liquid-filled vial containing a visible bubble whose position is read against a reference mark or target; a straightedge alone has no such indicator.
Confirm that the vial is mechanically related to a defined contact surface or mounting reference, so its indication can describe the orientation of something beyond the vial itself.
Check whether the measurement depends on observing a bubble, rather than solely on a projected laser line or an electronic angle display.
For a circular bubble indicator, determine whether it belongs to a standalone level or is an integrated component of another instrument; appearance alone does not settle the model boundary.
Scope
+ Identification through bubble vials and their relationship to reference surfaces
+ Supported checks for horizontal, vertical or specified inclined orientation
+ Reference-surface geometry and contact with the object being checked
+ Vial readability, bubble behaviour and interpretation
+ Accuracy evidence, reversal checks and condition affecting measurement
+ Attachments and handling constraints that affect placement or trustworthy use
- The geometry, condition and required tolerances of the workpiece or structure being checked
- Laser levels and optical surveying instruments as complete instruments
- Standalone electronic inclinometers and phone levelling applications
- Construction procedures for adjusting, fastening or accepting the measured work
- Manufacture and chemical formulation of vial liquid
- General workshop inventory and purchasing workflows
Characteristics
- Level form
- Examples: box, I-beam, torpedo, line, post, circular; other or unknown The form determines how the tool is supported and which placement methods are appropriate.
- Vial arrangement
- Number, geometry and fixed or adjustable orientation of bubble vials An agent must identify which vial supports each intended check.
- Supported reference orientations
- Horizontal, vertical, specified incline or adjustable incline; record supporting evidence A centred bubble has meaning only in relation to the selected vial and its intended orientation.
- Reference-surface extent
- Contact length and width in mm, or documented mounting geometry The contact extent determines which portion of the measured object contributes to the indication.
- Vial-to-reference relationship
- Each vial linked to its intended working face, edge, suspension or mounting reference Using an unsupported face can make an apparently clear indication misleading.
- Declared accuracy
- Manufacturer-stated error in mm/m or angular units, with applicable orientation and conditions; unknown if unverified Suitability depends on comparing supported accuracy with the task tolerance.
- Vial sensitivity
- Tilt per bubble displacement or division, with units and source; unknown where unspecified Sensitivity affects how small a change can be observed and must not be treated as equivalent to accuracy.
- Reference-surface condition
- Clean and apparently intact, contaminated, burred, worn, distorted or unassessed Contact defects can alter the orientation reported by the tool.
- Vial condition and readability
- Record bubble integrity and movement, liquid visibility, window clarity, markings and mounting security An indication cannot be trusted if the bubble or its reference cannot be read consistently.
- Verification status
- Unchecked, consistent under a recorded check, discrepant or inconclusive; include date, method and orientation A past check supports only the functions and conditions it actually examined.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 16 findings · 24 questions.
Bubble and reference identity Establish what makes the object a spirit level and how its indicators relate to physical references.
A bubble alone does not establish what orientation the complete tool can measure.
Level form and boundary
Identify the physical form and whether the level is standalone or part of another instrument.
Bubble-based level identification
Record the observable bubble indicator, reference markings and tool boundary that support identification.
- What visible vial, bubble and reference markings identify this object as a spirit level? definition
- Is this a standalone tool, a removable level accessory or an integral indicator owned by another instrument? boundary
Vial to working reference
Map each vial to the face, edge or mounting arrangement whose orientation it indicates.
Supported vial-reference pairs
Record supported vial and reference combinations without assuming every external face is a measuring surface.
- Which working face, edge, suspension or mounting reference corresponds to each vial? definition
- What marking, manual or other evidence establishes that each combination checks horizontal, vertical or a specified incline? provenance
Placement and contact Describe how the level acquires the orientation of the object being checked.
A sound vial can give an unsuitable reading when the level rocks, bridges a defect or is attached incorrectly.
Working-surface contact
Assess the actual contact supporting a reading.
Contact extent and stability
Record the selected reference surface, effective contact extent and evidence of stable seating.
- Which part of the workpiece is sampled by the level's actual contact points or contact length? measurement
- Must debris, rocking or a local obstruction be resolved before the reading can represent the intended surface? action
Special placement features
Identify design-specific support such as magnets, pipe grooves, hooks or post attachments.
Attachment-supported placement
Record how an attachment supports the tool and whether it preserves the intended measuring reference.
- Which attachment or shaped contact feature is present, and what workpiece or support is it intended to engage? definition
- How can the agent confirm that the attachment holds the level stably with its intended reference correctly engaged? action
Bubble reading and interpretation Connect an observed bubble position to a justified orientation statement.
The agent must distinguish a readable indication from an unsupported numerical or pass/fail claim.
Observable bubble indication
Assess whether bubble position can be observed consistently against the intended reference.
Readable settled position
Record bubble position together with viewing conditions and any ambiguity in reading the markings.
- Where is the settled bubble relative to the relevant lines or target under the recorded placement? measurement
- Does changing the viewing position alter the apparent reading enough to require a better view or an inconclusive result? action
Meaning and resolution
Determine what the vial markings and available performance evidence allow an agent to infer.
Supported orientation conclusion
Separate centred or displaced observations from calibrated slope estimates and task acceptance decisions.
- What documented meaning do the centre marks, graduations or adjustable-vial setting have on this particular level? provenance
- Does the available sensitivity and accuracy evidence support a numerical slope estimate, a qualitative orientation statement or neither? boundary
Trustworthiness and use decisions Assess damage, verification evidence and the level's suitability for a proposed measurement.
Recognising a spirit level is insufficient when its reference surfaces or vial alignment may have changed.
Physical measurement integrity
Inspect defects that could corrupt contact, vial alignment or bubble observation.
Defects affecting indication
Record surface distortion, contamination, loose vial mounts, damaged windows and abnormal bubble behaviour as separate observations.
- What observable defects affect the working reference, vial security, liquid enclosure or readability? measurement
- Which observed issues permit cleaning and rechecking, and which require repair, replacement or withholding the tool from the proposed use? action
Verification and task fitness
Use documented checks and accuracy evidence to bound confidence in each supported function.
Orientation-specific verification
Record the reversal or reference-comparison procedure, its result and its limits without treating a consistency check as complete calibration.
- Under a suitable documented reversal or reference comparison, how closely do the indications agree for the vial and working face being assessed? measurement
- Given the check result, applicable accuracy evidence and required task tolerance, may this level support the proposed decision or is further verification needed? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Box-beam carpenter's level (hollow rectangular extrusion, typically with horizontal and plumb vials)
- I-beam carpenter's level (open-web extruded or formed beam)
- Torpedo level (short pocket or magnetic body, often with 0°, 90° and 45° vials)
- Line level (lightweight vial that hangs on a taut string)
- Circular / bullseye level (domed vial indicating two-axis level at once)
- Precision / engineer's / machinist's level (ground cast-iron or steel base, high-sensitivity vial)
- Post / column level (wrap-around or three-face body for squaring a post)
- Electronic / digital box level (display of angle, often still fitted with conventional vials)
- Which of these kinds and varieties hold for the sense of spirit level this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q19050 - Item for the spirit / bubble level as a measuring instrument.
- Which of these identifiers and schemes hold for the sense of spirit level this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- DIN 877 (Deutsches Institut für Normung) - Libellen / spirit levels, including vial sensitivity in mm/m.
- JIS B 7510 (Japanese Industrial Standards Committee) - precision levels for machine-shop use.
- BS 3509 (British Standards Institution) - spirit levels for precision engineering (historical/withdrawn in current catalogues, still the English-language product standard most often cited).
- Building and execution codes (for example Eurocode/EN 13670 geometric tolerances, or national residential codes) govern how level and plumb the finished work must be; they do not type-approve the hand tool.
- Which of these standards and regulation hold for the sense of spirit level this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- A carpenter or drywaller sets a 600 mm or 1200 mm box level on a shelf, frame, or wall to bring a course or edge to horizontal, then turns it on end to plumb a stud or jamb.
- A bricklayer or landscaper hangs a line level on a taut string to keep a foundation, fence, or course consistent over a span longer than the tool.
- A machinist parks a precision block level on a lathe bed, surface plate, or machine-tool table and reads residual twist in mm/m or arcseconds.
- Camera, theodolite, and appliance installers use a bullseye vial to get a tripod or cabinet into two-axis level before fine work.
- Electricians and fitters use a magnetic torpedo level on conduit, switch gear, and steel studs.
- Which of these real-world use hold for the sense of spirit level this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Body length - 200-2000 (torpedo ~200-250; common carpentry 600 and 1200; long box beams to 2000) - mm
- Vial sensitivity (tilt that moves the bubble a stated mark, often 2 mm) - 0.5-1.0 for trade carpenter's levels; 0.02-0.10 for engineer's/precision levels - mm/m
- Indicated accuracy of a trade box level - ±0.3 to ±1.0, commonly stated as ±0.5 - mm/m
- Number of vials - 1-3 (level, plumb, sometimes 45°); bullseye is a single two-axis vial - count
- Working temperature of the vial fill - about −20 to +50 for modern trade vials; precision work is done near the calibration temperature - °C
- Which of these typical measurements hold for the sense of spirit level this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Vial leak or evaporation of the fill (historically ethanol or ether; still a flammable or irritating liquid in some vials) so the bubble grows or the vial empties and the reading is lost.
- Permanent bend or twist of the frame after a drop or from heat, so both vials can read 'in' while the reference face is no longer coplanar.
- Thermal gradient along the vial or body (sun on one flange, cold floor on the other) shifting the bubble without a true tilt.
- Parallax or dirty/yellowed acrylic vials causing a false centre reading.
- Frozen or highly viscous fill in cold weather, so the bubble is sluggish or stuck.
- Broken glass vials (cut hazard) on older or precision instruments; acrylic trade vials crack rather than shard.
- The tool does not itself injure by measurement error, but a false 'level' on a scaffold, rack, or machine bed produces unstable or out-of-tolerance work.
- Which of these failure modes and hazards hold for the sense of spirit level this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- In British and Commonwealth trade speech the instrument is a spirit level; in North American hardware speech it is more often a bubble level, carpenter's level, or simply a level.
- German Wasserwaage / Libelle, French niveau à bulle, Spanish nivel de burbuja, Italian livella a bolla name the same vial instrument; 'Libelle' in German shop standards is specifically the vial.
- In surveying English, 'level' usually means a telescopic automatic or digital height instrument, not a carpenter's spirit level - a naming collision that is stronger in the field than in the hardware aisle.
- Trade bodies are commonly marked in millimetres in Europe and in inches in the United States; the vial physics are the same.
- Japanese and German machine shops treat the precision block level as a calibrated inspection tool (JIS B 7510 / DIN 877 classes); many English-speaking building sites treat the box level as a consumable layout aid.
- Which of these regional variation hold for the sense of spirit level this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Laser level (line, rotary, or dot) - A laser level indicates a plane by projected light, usually from a pendulum or electronic compensator. A spirit level indicates only at the tool, by a bubble in a curved vial. If the indication remains after the beam is switched off, it is the spirit level.
- Water / hose level - A hose level uses two open columns of liquid in communicating vessels and reads a common free surface over a long run. A spirit level is a sealed, locally curved vial and does not transfer a datum through a hose.
- Surveyor's automatic, dumpy, or digital level - Those instruments take a telescopic or electronic height reading to a staff; a circular spirit vial, if present, is only for rough setup. The test is whether the primary output is a staff reading or a bubble against vial marks.
- Inclinometer / digital protractor / clinometer - An inclinometer reports a continuous angle. A spirit level reports whether the bubble is between marks (in-level / out-of-level), even when a digital box level also prints degrees - if the sensing element is a MEMS inclinometer with no functional vial, it is not a spirit level.
- Plumb bob - A plumb bob indicates vertical by a hanging mass and string. A spirit level indicates vertical only when a plumb vial is set against the member; it has no free hanging mass.
- Straightedge - A straightedge tests coplanarity or straightness against a surface and has no gravity reference. A spirit level can read 'true' on a bowed surface if the vial happens to sit level.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of spirit level this model covers, and on what evidence? provenance
Sources
- Spirit level - Wikipedia (Wikimedia Foundation) - Instrument principle (curved vial and bubble), common English names, carpenter versus precision forms, and distinction from surveying levels.
- DIN 877 Libellen (spirit levels) - Deutsches Institut für Normung - The millimetre-per-metre sensitivity convention used for trade and precision vials, and the existence of a national product standard for the instrument itself.
- JIS B 7510 Precision levels - Japanese Industrial Standards Committee - Precision/engineer's block levels as a distinct, specified shop instrument rather than a carpenter's layout tool.
- Machinery's Handbook - Industrial Press - Shop practice for precision spirit levels on machine beds and surface plates, including sensitivity expressed as bubble travel versus tilt.
What the second pass must settle
- Does the registry intend spirit level to include standalone circular, line and post levels, and how should integrated bubble indicators be linked to their host models?
- Which authoritative references establish reversal-check procedures and acceptance criteria for the different vial orientations and level forms?
- How do manufacturers specify accuracy for normal, inverted and vertical use, and which distinctions must this model preserve?
- Which vial markings support quantitative slope readings, and how should sensitivity be represented when markings only indicate centring?
- What manufacturer-specific limits govern temperature, bubble condition, adjustable-vial checks and permissible repair or adjustment?