Switchblade

A switchblade (also known as an automatic knife, pushbutton knife, ejector knife, switch, Sprenger, Springer, flick knife, or flick blade) is a type of knife with a folding or sliding blade contained in the handle which is opened automatically by a spring when a button, lever, or switch on the handle or bolster is activated. Most switchblade designs incorporate a locking blade, in which the blade is locked against closure when the spring extends the blade to the fully opened position. The blade is unlocked by manually operating a mechanism that unlocks the blade and allows it to be folded and locked in the closed position.