To get the greatest benefit from jigs and fixtures, a basic understanding of their construction is necessary. Jigs and fixtures are identified one of two ways: either by the machine with which they are identified or by their basic construction. A jig, for instance, may be referred to as a “drill jig.” But if it is made from a flat plate, it may also be called a “plate jig.” Likewise, a mill fixture made from an angle plate may also be called an “angle-plate fixture.” The best place to begin a discussion of jig and fixture construction is with the base element of all workholders, the tool body.