> ## Documentation Index
> Fetch the complete documentation index at: https://support.lumafield.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Perpendicularity

> GD&T perpendicularity of a plane or cylinder to its datums

Perpendicularity constrains how square a face or an axis is to its datums. In ASME Y14.5 it is an orientation tolerance: the surface must lie in a zone that is exactly 90 degrees from the primary datum. It does not locate the feature. A face can be perfectly square to datum A and still sit in the wrong place; that location is [Position](/voyager/voyager-position) or a [Direct Dimension](/voyager/voyager-direct-dimensions).

Perpendicularity is in the Toolbar in [Dimensioning Mode](/voyager/voyager-modes#dimensioning-mode).

<h2 id="which-features">
  Which features it accepts
</h2>

* A **plane** — a face that should be square to the datum.
* A **cylinder** — a hole or a pin whose axis should be square to the datum.

The primary datum can be a plane, a midplane, or an axis. A secondary datum is allowed only when it clocks the zone: a plane feature whose primary is a plane or a midplane. In that case the secondary is itself a plane datum, and it is optional. A tertiary datum is not used. Every other combination refuses the extra datum rather than ignoring it.

<h2 id="the-tolerance-zone">
  The tolerance zone
</h2>

The default zone is the space between two parallel planes, set square to the primary datum. The tolerance is the distance between those planes, in millimeters.

**Diametral zone (⌀)** is available for a cylinder whose primary datum is a plane or a midplane. The zone is then a cylinder around the true axis, and the tolerance is a diameter. A cylinder held the other way — across the datum rather than along it — stays a two-plane zone, and the diametral toggle is not offered.

<h2 id="workflow">
  Workflow
</h2>

<Steps>
  <Step title="Select Perpendicularity">
    Choose **Perpendicularity** from the Toolbar, or right-click a plane or cylinder and choose **Add perpendicularity control…**.
  </Step>

  <Step title="Pick the feature">
    Click the face or the cylinder to control. Eligible features highlight on hover.
  </Step>

  <Step title="Set the tolerance">
    Enter the tolerance. Turn on **Diametral zone (⌀)** when the control is a cylinder square to a plane datum and the drawing uses a diameter.
  </Step>

  <Step title="Select the datums">
    Pick the primary datum. Add a secondary plane datum only when the panel offers that rank.
  </Step>

  <Step title="Place the callout and submit">
    The callout section opens once a feature is picked. Submit to add the control to the feature set. Drag the leader to place the label.
  </Step>
</Steps>

<h2 id="reading-the-result">
  Reading the result
</h2>

The callout reports how far the feature leans out of the square zone, and whether that is inside the tolerance. **Measured in** names the datums. **Open freedoms** lists motion the datums did not stop. Edit the tolerance afterward; the pass or fail state updates without a new extraction.

<h2 id="related-pages">
  Related pages
</h2>

* [Parallelism](/voyager/voyager-parallelism)
* [Position](/voyager/voyager-position)
* [Flatness](/voyager/voyager-flatness)
* [Datum Definition](/voyager/voyager-datums)
* [3D Auto-Dimensioning](/voyager/voyager-auto-dimensioning)
* [Voyager Release Notes](/platform/voyager-release-notes)


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