Saps, blackjacks, twistjacks, billyclubs, lugshots are all passive impact weapons. Considered effective self defence weapons that are less lethal than knives or firearms. Depending on their size, weight and construction make them vary in their effectiveness and of course how lethal they could be.

Definitions as I see it;

Blackjack or Cosh - strong coil spring, sometimes ridgid, with a round bulbus end cast from lead, wrapped in leather, usually part or all braided. These vary in size and weight and have a round profile.

Sap - a flat or oval weight, traditionally lead but sometime flat steel sandwiched between leather. It has a flat profile. Sometimes sprung with a length of spring steel, sometime not.

Twistjack - length of braided wire rope with a round bulbus end cast from lead, wrapped in leather, smaller than a blackjack. Usually part or all braided. These vary in size and weight and have a round profile. There is no spring effect.

Billyclub - a short turned piece of wood, baton.

Slungshot - a fishing weight or similar small heavy object wrapped, often in leather or a sock, with a very thin extended handle, to allow it to be swung.

Coin Saps/Coin wallets - flat profile, with a zip to allow you to add coins to it to for the weight. As these have no fixed weight, they could also be called coin wallets therefore entering the area of legal carry and no one needs justification for carrying coins. 

Tow Hook Saps - a flat profile like a standard sap, but the weight is a bare tow hook. As its a hook you can clip it onto a belt loop, and the ones I have done enable you to carry your keys on the other end. Effectively just a handy heavy duty key ring.

Palm Saps - A small weight able to fit in the palm of the hand, secured in place by a strap over the back of the hand. More concealable than most other styles. Increases the effectiveness of an open hand slap, or can be used, if cylindical, to make a fist solid reducing the risk of injury to your hand when punching.

These have been around in various forms for over 200 years.  

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