Revision as of 23:59, 14 January 2026

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

Start here

Standard definitions, symbols, and usage guidance.

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

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.	Supporting rules and .

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

@@ Line 1: / Line 1: @@
-<!-- Copy into Main Page -->
 __NOTOC__
 = F4 Wiki =
@@ Line 13: / Line 12: @@
 == Start here ==
-{| style="width: 100%; border-collapse: separate; border-spacing: 12px;"
+{| class="f4-card-grid"
 |-
-| style="vertical-align: top; width: 33%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Category:GDT Reference|GD&T Reference]]'''
+<div class="f4-card-title">[[Category:GDT Reference|GD&T Reference]]</div>
-: Standard definitions, symbols, and usage guidance.
+<div class="f4-card-desc">Standard definitions, symbols, and usage guidance.</div>
-| style="vertical-align: top; width: 33%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Category:F4 Behavior|F4 Behavior]]'''
+<div class="f4-card-title">[[Category:F4 Behavior|F4 Behavior]]</div>
-: Rules, checks, and decisions used by the F4 validator.
+<div class="f4-card-desc">Rules, checks, and decisions used by the F4 validator.</div>
-| style="vertical-align: top; width: 33%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Category:Glossary|Glossary and Examples]]'''
+<div class="f4-card-title">[[Category:Glossary|Glossary and Examples]]</div>
-: Short definitions and worked applications.
+<div class="f4-card-desc">Short definitions and worked applications.</div>
 |}
 == Browse by category ==
-{| style="width: 100%; border-collapse: separate; border-spacing: 12px;"
+{| class="f4-card-grid"
 |-
-| style="vertical-align: top; width: 50%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Category:Form|Form]]'''
+<div class="f4-card-title">[[Category:Form|Form]]</div>
-: Straightness, flatness, circularity, cylindricity.
+<div class="f4-card-desc">Straightness, flatness, circularity, cylindricity.</div>
-| style="vertical-align: top; width: 50%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Category:Orientation|Orientation]]'''
+<div class="f4-card-title">[[Category:Orientation|Orientation]]</div>
-: Parallelism, perpendicularity, angularity.
+<div class="f4-card-desc">Parallelism, perpendicularity, angularity.</div>
 |-
-| style="vertical-align: top; width: 50%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Category:Location|Location]]'''
+<div class="f4-card-title">[[Category:Location|Location]]</div>
-: Position, composite, MSS, concentricity, symmetry.
+<div class="f4-card-desc">Position, composite, MSS, concentricity, symmetry.</div>
-| style="vertical-align: top; width: 50%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Category:Profile|Profile]]'''
+<div class="f4-card-title">[[Category:Profile|Profile]]</div>
-: Line, surface, composite, MSS.
+<div class="f4-card-desc">Line, surface, composite, MSS.</div>
 |-
-| style="vertical-align: top; width: 50%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Category:Runout|Runout]]'''
+<div class="f4-card-title">[[Category:Runout|Runout]]</div>
-: Circular and total runout.
+<div class="f4-card-desc">Circular and total runout.</div>
-| style="vertical-align: top; width: 50%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''Supporting rules'''
+<div class="f4-card-title">Supporting rules</div>
-: [[Category:Modifiers|Modifiers]] and [[Category:Datums|Datums]].
+<div class="f4-card-desc">[[Category:Modifiers|Modifiers]] and [[Category:Datums|Datums]].</div>
 |}
@@ Line 65: / Line 64: @@
 == Community ==
-{| style="width: 100%; border-collapse: separate; border-spacing: 12px;"
+{| class="f4-card-grid"
 |-
-| style="vertical-align: top; width: 50%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Forum:Start|Community forum]]'''
+<div class="f4-card-title">[[Forum:Start|Community forum]]</div>
-: Announcements, questions, feature requests, and showcases.
+<div class="f4-card-desc">Announcements, questions, feature requests, and showcases.</div>
-| style="vertical-align: top; width: 50%; padding: 0.9em; background: var(--f4-bg-panel); border: 1px solid var(--f4-border); border-radius: 10px;" |
+| class="f4-card" |
-'''[[Special:UserBoard|Messages]]'''
+<div class="f4-card-title">[[Special:UserBoard|Messages]]</div>
-: Direct messages between contributors.
+<div class="f4-card-desc">Direct messages between contributors.</div>
 |}