Sling means in the bible: We associate the shepherd’s sling with David 1 Sam. 17:40-50, and the men of Benjamin Judg. The pad for 20:16 consisted of two leather thongs or strings attached to it. A pad was used to hold the stone. It could be made from leather or woven material. Many thongs had loops that one could insert his fingers. The sling was to be wrapped around one’s head using a small stone that had been placed into the pad. The stone will fly to its mark if one string is let go. This method can be very precise if you practice. Three-inch diameter Flint slingstones were found. Also see 2 Kgs. 3:25; 2 Chr. 26:14.
(in Bible Dictionary)