The polymer frame makes them lighter than typical steel or aluminum-framed handguns, an attractive feature for police officers and regular citizens who carry firearms for extended periods of time. The trigger is the only operating element; all three safeties are deactivated when the trigger is pulled, and automatically activated when it is released. Glock pistols have no other manual safeties (as some other brands have a lever or button); the only external controls aside from the trigger itself are the slide stop lever, the magazine catch, and the slide lock for disassembly. This adds to the simplicity of use and removes a potential source of error while operating the handgun under stress. Most of the steel components in a Glock pistol are treated with a nitriding process called "Tenifer", which increases the surface hardness and makes the pistol resistant to corrosion and wear.