<p>This disclosure relates to a combination square comprising a blade and a body. A lock permits the blade to slide relative to the body in an unlocked configuration and locks the blade with respect to the body in a locked configuration. The combination square also comprises a removable extension bracket being wider than and removable from the body and comprising one or more working surfaces. Certain embodiments also comprise a locking mechanism with a clamp subassembly comprising a cam follower portion. Other embodiments also comprise a scribe guide adapted to locate on the blade, the scribe guide having an aperture for receiving a scribe in use.</p>
