Buttstocks or gun stocks, are parts, (either built-in or attachable) on a rifle, that the wielder positions against his/her shoulder for support when firing the rifle. Some stocks are built onto the rifle, and cannot be removed, where as some stocks can either be removed, or folded down. Some of the first stocks to be used were in matchlock rifles. In some assault rifles(such as the Colt M4), stocks are collapsable, for versatility in combat. Nowadays, some of the buttstocks (such as the FN SCAR-L, FN SCAR-H and the Remington ACR) have adjustable cheekpieces and foldable buttstocks, which increases mobility and stability.