Cap shanks are small holders that the female or male cap is attached to using a taper. This shank usually has a full size RWMA taper on its other end which is used to attach it to the holder mechanism on the machine, cylinder or servo.
The shanks can be straight or bent. The bends are single and double bends to reach over or into restricted areas of a part. They shanks are normally the same diameter as the electrode. Shanks serve as adapters between the machine and the electrode cap.
In the case of weld guns the shanks are referred to as adapters and are much larger in diameter and carry much higher forces than the shanks described above.
Reference: Tuffaloy Resistance Welding Products Catalog