Restraining bolts were small, cylindrical devices that could be affixed to a droid in order to limit its functions and enforce its obedience. When inserted, a restraining bolt restricted the droid from any movement its master did not desire, and also forced it to respond to signals produced by a hand-held control unit known as a caller. Some droids felt sheer horror at the mere mention of restraining bolts. Restraining bolts were also used in the construction of Jawa ion blasters; they, along with accu-accelerators from a starship‘s ion engine, were fitted to the blaster‘s firing mechanism.
Droids could not remove restraining bolts from themselves.. In one exception to this rule, however, the droid L3-37 removed several restraining bolts from other droids during a revolt of slaves and droids on Kessel.
Sabine Wren would sometimes threaten Chopper with a restraining bolt when he was uncooperative.