Another old design is the shoulder vise. The best thing about this design is that it allows clamping directly behind the screw. This yields unobstructed vertical clamping for cutting dovetails and similar operations. There is also typically a little play in the screw/jaw attachment that provides for clamping of tapered work. This is one vise that should be designed into the bench from the beginning, as it is difficult to retrofit into an existing bench. The primary drawback of the shoulder vise is its fragility, unless the "arm" is attached to the "end cap" using a dovetail or finger joint, usually glued or "pinned" to eliminate rotative movement about the joint, otherwise it is fairly easy to break it with a big steel bench screw. But one should never really have to put "that" much force on it. Some woodworkers say that the big vise gets in the way of some jobs, others find it unobtrusive. Implicit in a shoulder vise is an integral planing stop, formed by the intersection of the jaw and the jaw spacer, and which allows the shoulder vise to perform multiple duties, such as jointing long boards with a "bench slave" to hold the opposite end. In earlier times, a "crochet" and a holdfast would perform the same function.