Abstract: A pouch-like holder for a triangular carpenter's square includes a single sheet of flexible material which is folded in half to form two congruent panels, each in the shape of a truncated triangle, with the side edges opposite the fold line being secured together along a closure line disposed at about a 45.degree. angle to the fold line to define a triangular pocket having a large open top and a small open bottom for receiving the square therein. Belt slits are provided in each of the panels and a retainer strap is also provided across the top edges of the panels. The holder also has alternative closures and belt attachment devices.