Leather saps or "blackjacks" as they are also known have been used by law enforcement for generations. It has a thick leather outer skin that is sewn around flexible steel handle and has molded lead in the striking end. The steel keeps the unit rigid but allows a little give when you strike something. saps are flat and slip right into a pants pocket almost un-noticed. This was a very effective weapon when law enforcement use to carry them. In fact, many police departments had a special pocket built into the officer's uniform. It was usually down the side of the leg and would allow the leather strap to hang out.
Durable, heavy gauge leather encases molded lead weight with spring steel shank. Both 2-ply and extra thick 4-ply models are available.