曲尺是木工或金属加工工具，一边长一边短的直角尺。，用于衡量一个标记和一块木头 。这个工具的主要用途测量精度直角（90度）的表面。有些角尺上标示公制或英制刻度以方便测量。

A try square is a woodworking or a metal working tool used for marking and measuring a piece of wood. The square refers to the tool's primary use of measuring the accuracy of a right angle (90 degrees); to try a surface is to check its straightness or correspondence to an adjoining surface. A piece of wood that is rectangular, flat, and has all edges (faces, sides, and ends) 90 degrees is called four square. A board is often milled four square in preparation for using it in building furniture.