In SOLIDWORKS, relations between sketch entities and model geometry, in either 2D or 3D sketches, are an important means of building in design intent.
You can add relations in the following ways:
- As you sketch, allow the SOLIDWORKS application to automatically add relations. Automatic relations rely on:
- Inferencing
- Pointer display
- Sketch Snaps and Quick Snaps
-
After you sketch, manually add relations using the Add Relations
tool, or edit existing relations using the Display/Delete Relations 
tool.If you right-click with one or more sketch entities selected, the toolbar that displays stays visible to allow you to add multiple relations. For example, if you have two lines selected, you can you can add vertical and parallel relations to the lines and make them equal without having to make changes in the PropertyManager or redisplay the toolbar.
Equations create mathematical relations between model dimensions, but outside of sketches.