The non-reciprocating charging handle on the top of the receiver cover is used to retract the bolt. Variants have a ratchet safety mechanism which will catch the bolt and lock its movement if it is retracted past the magazine, but not far enough to engage the sear. When the handle is fully retracted to the rear, the bolt will cock (catch) on the sear mechanism and the handle and cover are released to spring fully forward under power of a small spring. The cover will remain forward during firing since it does not reciprocate with the bolt. The military and police versions will fire immediately upon chambering a cartridge as the Uzi is an open bolt weapon.