The Onshape sketch editor has the ability to assign constraints to certain entities automatically. For example, create a line and hover one of the endpoints above the origin and a dotted line appears indicating a vertical inference between that endpoint and the origin.

When sketching, Onshape displays inferences for Horizontal and Vertical alignment between an entity and the origin and/or another entity. In some cases, inference only occurs when the cursor is moved near another entity to 'wake up' the inferencing between the two entities. Some commonly used wake up inferences are: horizontal, vertical, midpoint, parallel, and coincident.


  1. Create two lines with a perpendicular constraint between them.
  2. Move cursor near line until inferencing ‘wakes up’.
  3. Draw a line.

Steps to using Automatic Inferencing tool

When sketching, Onshape indicates relationships with other sketch entities. In the illustration below, the bottom (blue) line is the one being drawn. When it is parallel to the other line it turns to a dotted line and the other is highlighted in orange to show that there is a relation present. (The parallel constraint icon is also visible in this example.)

Example of two lines showing their relation to one another

To suppress automatic inferences, press the Shift key when mousing.