Abstract: The apparatus forms a combined locating pin and gage for supporting and measuring two pieces of an assembly. The method for using the apparatus includes measuring an opening within each piece of the assembly using the limit gage portion of the apparatus and then locating the pieces together to form a temporary assembly using the gage as the shank of the locating pin portion of the apparatus. The apparatus includes a handle and a shank extending from the handle. In order to use the locating pin and gage apparatus, the mid-section of the shank forms a limit gage and has an outer diameter of a fixed dimension for measuring an opening within the two pieces of the assembly. If the diameter of each opening is within the predetermined limit set for the openings, then the handle of the apparatus is rotated in either direction, correspondingly rotating the lower locking section and causing the locking section to contact the lower piece, effectively temporarily and positively locking the assembly together.