Abstract: A carpenter's square is provided which is uniquely configured for use in the construction of a building which utilizes metal framing members. The square is adapted to enable a steel wall stud to be aligned and oriented relative to a steel track to which the stud is to be fastened, and thereafter maintained in proper alignment while the stud is being secured to the track. The square includes a pair of detachable legs. One leg has an inner longitudinal edge formed with a longitudinal recess which extends across the entire width of the edge, such that a gap is created between the leg and a planar surface abutted against the edge of the leg. The longitudinal recess accommodates a portion of the track which extends over the stud, as well as the head of a fastener used to secure the stud to the track. To stabilize and secure the square to the wall stud, at least one of the legs is equipped with a magnetic portion which magnetically adheres the leg to the stud or track.