Main Page

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.

Quick links

• F4 website
• Documentation
• Downloads

Start here

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

Form Straightness, flatness, circularity, cylindricity.	Orientation Parallelism, perpendicularity, angularity.
Location Position, composite, MSS, concentricity, symmetry.	Profile Line, surface, composite, MSS.
Runout Circular and total runout.	Supporting rules Related guidance for modifiers and datum systems. Modifiers Datums

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

Community forum Announcements, questions, feature requests, and showcases.

Messages Direct messages between contributors.

Contribute

• Contributor guide
• License
• Review queue