Designed for toolmakers, the American made Starrett 14MD is perhaps the finest small square manufactured anywhere in the world.
The stock and blades are made from hardened and ground steel for long lasting accuracy. The clamping mechanism that engages in the slot of the blade slides up and down under a light spring pressure but doesn't rotate (Starrett's second patent) so it is quick and easy to change blades.
In fine cabinetmaking, the narrow blade is particularly useful for checking things that you couldn't reach with an ordinary square - like the internal faces of dovetails or bridle joints.
Complete with graduated standard blade, graduated narrow blade and bevel blade.
Standard blade is 50mm long, 12.7mm deep and 1.4mm thick
Beveled blade is 45º on one end and 30º on the other. 2-1/4" (58mm)
Narrow blade has mm and 1/2mm graduations. It is 4mm wide over a length of approximately 41mm and cut away at one end to a width of just 2.4mm