A try square is used in carpentry or woodworking to test for a perfectly straight cut, usually at the end of a board. L-shaped, the try square has a flat metal blade set at a right angle to its thick wooden handle.
You hold the handle snugly against a board’s edge and align the blade with the board’s end. Any variance from a perfectly straight, “square” (90-degree) edge becomes evident as light showing between the blade and the board.
The try square can also be used to mark a 90-degree line across a board. One variation, the try/miter square, has a 45-degree angle along the handle to allow for testing or marking miters.
Of pre-15th-century French or English origins, the word “try” means to pick or select. In the 17th century, it took on the meaning of true or well wrought in wood joinery. The first reference to a square appeared in 1877.