Abstract: An instrument used to establish precise perpendicular quill (32) alignment with respect to the work table of vertical milling machines with adjustable head assemblies (34). This instrument incorporates three basic tools into one device: (a) an internal cylindrical square; (b) a straight collet with flanged base; (c) a horizontal crosstest level with two vials at right angles to each other. This instrument is designed to be used on machines which have been set on concrete foundations, leveled, and then grouted to machine manufacturers specifications. The squaring process includes first setting the instrument flange (10) down on the work table directly under the quill (32). The quill is then telescoped into the collet bore (18) and the collet closing block (20) is then locked by bolt (20B). The position of the crosstest vial readings (24L) and (24F) are then noted and the head alignment bolts (30F) and (30A) are manipulated to establish a level condition.