A rugged, cast iron square head that will outlast cheap plastic and die-cast imitations An accurate, hardened and tempered square blade offered in inch, millimeter, and inch and millimeter combined Reversible lock bolt allows the blade to be turned over or end-for-end so that all four graduated edges may be used The combination square can be used as a try square, 45° miter, a depth gage, a height gage, a layout tool, and as a rule An optional center head is available to increase the versatility of this universal measuring tool 4 graduated edges For training "youngsters" and apprentices to lay out and check their work more efficiently.