Collinear

Short Answer

Yes — in SolidWorks, you can make sketch entities collinear by adding a Collinear relation in a 2D sketch. The fastest professional method is to Ctrl-select two parallel lines, then use Add Relations in the PropertyManager. This only works on valid sketch entities that can share a straight-line direction.

What You Need to Know Before

Warning: If the lines are not parallel-capable or one entity is already over-defined by other sketch relations, the collinear relation may fail or create a sketch error. This is especially common in imported geometry or fully constrained sketches.

How to Make Entities Collinear in SolidWorks

• Command: Add Relations

• Shortcut: No default keyboard shortcut

• Quick Steps:

  1. Edit the sketch, then Ctrl-select the two sketch lines in the graphics area.
  2. In the left PropertyManager under Add Relations, click Collinear.
  3. Click the green checkmark to confirm, and review if Fully Define Sketch status changes or any over-defined warning appears.

Variables & Settings

• Key Setting: Add Relations > Collinear

  This relation forces selected sketch lines to lie on the same infinite line. If the entities already have conflicting relations such as Horizontal, Vertical, Parallel, or fixed endpoints, SolidWorks may reject the relation or over-define the sketch.

Why it Fails

• Cause 1 (Geometry): One selected entity is not a compatible sketch line, or the geometry cannot mathematically align into the same straight line.

• Cause 2 (layers/Locks): The sketch entity may be fixed, locked by external references, or imported as constrained geometry that cannot accept the new relation.

• Cause 3 (Command/Logic): Too many existing relations or dimensions already define the entity position, so adding Collinear over-defines the sketch.

Quick Fix & Best Practice

• Quick Fix: Use Display/Delete Relations to remove conflicting sketch relations, then reapply Collinear through Add Relations.

• Manager’s Verdict: Use Collinear for clean parametric sketch control when aligning multiple lines. Avoid stacking it with unnecessary dimensions or redundant relations in production models.

FAQ

Can I make three lines collinear at once?
Yes, if all selected sketch lines are compatible, you can apply the relation to multiple lines together.

Does Collinear work on 3D sketches?
Not reliably in the same way as 2D sketch workflows; standard 2D sketch use is the most common method.

Why is Collinear grayed out?
Usually because the selected entities are incompatible or already constrained by conflicting relations.

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