The Perpendicular Snap tool is one of several Snap Tools . The command becomes available whenever the current prompt in the 3D CAD designer is for the selection of a 3D point while the cursor is currently manipulating an active object .
The purpose of the perpendicular snap tool is to snap the active part perpendicular (i.e. at 90 degrees) to one of its linked object center lines (or construction lines). The operation of the command is identical to the Angle Snap Tool except that it does not prompt for an angle, but uses a relative angle 90 degrees.