角尺是金属加工工具，两边一样长的直角尺。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。

• 《机械测量入门》，安改娣,格日勒，化学工业出版社，ISBN：9787122009180 / 7122009181

The steel square is a tool that carpenters use. They use many tools to lay out a "square" or right-angle, many of which are made of steel, but the title steel square refers to a specific long-armed square that has additional uses for measurement, especially of angles, as well as simple right-angles. Today the steel square is more commonly referred to as the framing square. It consists of a long arm and a shorter one, which meet at an angle of 90 degrees (a right angle). It can also be made of metals like aluminum, which is light and resistant to rust.