Fixture is a device that plays an auxiliary role in the machining process, used to fix the workpiece to be machined and guide the machining operation. It is also known as an auxiliary tool. For example, if a workpiece with a curved back is placed on a flat workbench and fixed with screws, it is difficult to effectively fix the workpiece. If the operation is not careful, the screw may be inserted at a certain angle. In this case, if a tool that fully conforms to the surface shape of the workpiece is used for auxiliary fixation, the workpiece will become stable and easier to operate. This is the foundation of the fixture concept. In addition to fixing workpieces, fixtures also have many other functions, such as ensuring stable quality and improving processing efficiency. There are mainly two types of fixtures. One is the various shaped fixtures used on the processing production line, and the other is the fixtures that fix the workpiece on the machine tool during the processing. Due to the fact that fixtures are unique products tailored to the processing content and object, they are not mass-produced or sold. Usually, it is made one by one by technical personnel from the production technology department and professional fixture manufacturers according to the usage method.

Compared to the phenomenon of different shapes and materials of fixtures used on processing production lines, fixtures used on CNC and other machine tools are mostly made of sturdy and durable metal materials such as stainless steel. The size of the fixture varies depending on the type of processing, and some large fixtures even require the use of a crane for movement; The workpiece is not temporarily fixed with fixtures, but is fixed with high-strength bolts. In the above picture, the part that supports and fixes the workpiece being cut is a "fixture". In some cases, especially for fixtures used in CNC machines, many threaded holes are machined on the fixture, so that one fixture can correspond to multiple workpieces.