The dimensions for a form can be set in a number of ways:
Drag the 3D control arrows on a form until the dimension meets the required value. You can select an edge, point, or vertex to enable the 3D controls. Drag a 3D control arrow. As you drag the arrow, element dimension feedback is provided in the drawing area. See Manipulating Forms.
Temporary dimensions display on the surface of a selected form. You can make this dimension permanent by double-clicking the dimension and pressing Enter.