lug and drives the bolt rearward, allowing the system to cycle. The SPAS-12 has a magazine cut-off feature, which prevents the magazine from releasing a new round when the action is cycled. This allows the operator to load a different type of round into the chamber without first unloading the chambered round, and the second that would otherwise subsequently be released from the magazine. A unique feature of the folding-stock variants is the butt hook. With the stock extended, the hook can be pushed in and turned 90 degrees to the left or right, to fit under the user's forearm. This is to enable the shotgun to be fired with one hand; e.g. while abseiling/rappelling, or from a vehicle window while driving. The hook can be released from the buttplate completely by turning through 180 degrees. SPAS-12 models feature two safeties: (i) a lever style or push button style safety, and (ii) a "quick employment safety". Lever safeties were recalled by Franchi and were replaced through the importer American Arms in the early 1990s. There are two types of push-button safeties. The earliest version would release the hammer on safe up to 1/4in. of travel when the trigger was depressed; this would cause a lockup of the action that would require the user to re-lock the bolt assembly to the rear to reset the hammer and then reload the chamber. The later version installed a detent and machined hole in the trigger group frame to prevent an action lock; the detent would prevent the hammer from engaging when the trigger was depressed and would prevent an action lock from occurring. The quick employment safety, which is on the left side of the trigger guard, disconnects the trigger when put into safe mode. The quick employment safety can be disengaged with the trigger finger when ready to fire and is intended for competition or tactical use. A third safety type, a pistol grip safety similar to the later-developed SPAS-15, is known to have been developed by Franchi for the SPAS-12, however the pistol grip safety was not offered for sale to the general public. A B-Square rail mount for optics was available for a short time in the 1990s as an aftermarket accessory. The barrel of the SPAS-12 was externally threaded to accept a variety of attachments. The barrel is cylinder bored and spreads a normal shot charge to about 900mm