Mouse Constraints

The angle pairs they define can be used to lock the cursor at a particular drawing angle, by pressing Shift during input. The mechanism can only be engaged while drawing or editing an element, as indicated by the thick rubber band line shown in the Floor Plan or the ghosted element contour shown in the 3D Window. It temporarily locks the cursor’s polar angle value in the Coordinates Palette using one of the angle pairs defined in the Options > Work Environment > Input Constraints and Guides.
When the drawing direction is constrained by pressing Shift, a dotted line connects the unfinished element with the location of the cursor.
1.
Display the Control Box. (Window > Palettes > Control Box)