The drafting instrument of the invention (10) disclosed herein generally compromises a planar body in a quadrilateral, symmetrical form, having four perimeter sides (22,24,26 and 28), interconnected end to end to form a quadrilateral configuration and show an open space (40) in the interior of the body, and of which two pairs of sides are right angles to each other and positioned opposite and symmetrical to each other on the planar body. The instrument is provided in two primary embodiments, the...