collapsable or folding stocks are often seen on military-grade carbines, smg/pdws and their civilian-derived versions. a collapsible (or telescoping) stock makes the weapon more compact for storage, carrying and concealment, and is usually deployed just before shooting for better control. a butt hook, which is an attachment to the butt of the gun that is put under the shooter's arm to prevent the rifle from pivoting forward from the weight of the barrel is sometimes used in competitive rifle shooting. these stocks are also used on combat shotguns like the franchi spas-12 to allow the stock to collapse when not in use.