The L. S. Starrett Company is an American manufacturer of tools and instruments used by machinists, tool and die makers, and the construction industry. The company was founded by businessman and inventor Laroy Sunderland Starrett in 1880. The company patented such items as the sliding combination square, bench vises, and a shoe hook fastener. It makes precision steel rules and tapes, calipers, micrometers, and dial indicators, among others. In addition, Starrett manufacturers a wide variety of saw products including bandsaws, hole saws, jigsaws, amongst other power tool accessories and cutting tools. More recently, they have expanded their high-end metrology equipment solutions including optical comparators, vision systems, laser measurement, force and material measurement testing.

A combination square is a multi-purpose measuring and marking tool used in metalworking, woodworking, and stonemasonry. It is composed of a rule and one or more interchangeable heads that can be attached to the rule. Other names for the tool include adjustable square, combo square, and sliding square.