2D CAD drawing tools
Once you have set up your scale, you can use CADtools to create objects at that scale. CADtools drawing tools snap to CADgrids for greater precision. CADtools also supports numeric input in scale for the following units: pt, p, mm, cm, m km, in, ft, and mi. To create an object numerically, click once on the document with any of the CADtools drawing tools.

CAD Rectangle
To create rectangles, position the cursor at a corner and drag to the opposite edge. Hold down the shift key to create a square.

CAD ellipses work in the same manner.