The sa is a hieroglyphic sign meaning protection. It possibly represents the reed mat that would have sheltered herdsman or a type of papyrus life perserver for boatman. Regardless of it's origins it came, like the ankh or the tyet to be used as an amulet. It was incorporated in jewelry and on magic wands. It was often held by protector deities such as Bes and Taweret.

Taweret shown with the sa in her hand