Definitions for joint, lap
The Standard Electrical Dictionary
(a) In belting a joint in which the ends are overlapped, and riveted or otherwise secured in place. If made without reducing the thickness of the ends it is a bad joint for electrical work, as it prevents even running of machinery to which it is applied. Hence dynamo belts should be joined by butt joints, or if by lap joints the ends should be shaved off so that when joined and riveted, there will be no variation in the thickness of the belt. (b) In wire lap joints are made by overlapping the ends of the wire and soldering or otherwise securing. The Britannia joint (see Joint, Britannia,) may be considered a lap-joint.