F4 Wiki

The public, stable reference for GD&T and how the F4 Application interprets it.
Each topic pairs standard GD&T guidance with F4 validation behavior so you can move from definition to decision quickly.

GD&T Reference
Standard definitions, symbols, and usage guidance.

F4 Behavior
Rules, checks, and decisions used by the F4 validator.

Glossary and Examples
Short definitions and worked applications.

Browse by category

- straightness, flatness, circularity, cylindricity.
- parallelism, perpendicularity, angularity.
- position, composite, MSS, concentricity, symmetry.
- line, surface, composite, MSS.
- circular and total runout.
and for supporting rules.

Featured pages

GDT:Straightness - basic line element form control.
GDT:Flatness - planar form control.
GDT:Position - primary location control for features of size.
GDT:Profile of a Surface - shape and location combined.
F4:Position Validation - how F4 checks position.

How to use this wiki

The public view shows approved revisions only.
Each GD&T page links to its matching F4 validation page.
Use the sidebar or search to find topics quickly.
When a rule needs interpretation, the F4 page calls out the decision and its impact.

Community

About F4

F4 is an engineering platform focused on GD&T interpretation and compliance checks. Use this wiki alongside the official docs and downloads.

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