Sap

A sap, also known as a slapper, slap jack, or beavertail sap, is a light, martial melee weapon that does non-lethal damage.

Description
A sap is a lead rod or disk hammered somewhat flat and wrapped in leather, then fitted to a spring handle. The handle may be an actual spring or a flexible strip of steel. Lead shot (small pellets) can also be used instead of a solid piece of lead. A typical sap costs 1gp and weighs 2lbs (0.9kg).

Weaponology
A sap is intended to deliver a non-killing blow, dealing out non-lethal damage for roughing someone up or knocking them unconscious. Knowing where to strike and getting in close enough to use a sap requires some skill and therefore the sap is considered a martial weapon. It is very difficult but not impossible to kill using a sap (or other non-lethal attack) by striking in the most vulnerable areas.