A straight cap shank is the most common. However in some applications one cannot reach into the proper location on the part without some adaption of the cap shank. A double bend cap shank solves many of these applications.
With the double bend the cap and shank can reach over or around some physical portion of the part and make a good weld without any skidding of arcing. Double bend shanks are available for either female or male cap.
Reference: Tuffaloy Products Resistance Welding Catalog