Switchblade

A switchblade (also known as an automatic knife, pushbutton knife, ejector knife, switch, Sprenger, Springer, or, in England only, flick knife) 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 (often confused with a different type of knife, the spring-assist or assisted-opening knife). A manually operated safety device fitted to most switchblades prevents the blade from opening in the event the button is accidentally pressed. 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.

The switchblade or automatic knife is thought to have originated as a response to demands for a convenient pocket knife that could be opened with only one hand. With the advent of mass production, which enabled folding knives to be produced at lower cost, distribution of such knives became much more widespread, with some manufacturers turning out thousands of automatic knives annually. While not as popular as traditional pocket or folding knives, the switchblade enjoyed a devoted if modest continuing popularity as a general utility knife. With the advent of legislation restricting ownership or sale of such knives in the mid-20th century, the worldwide popularity of the automatic knife began to decline. Today most switchblades are produced by small knifemaking companies on a semi-custom basis for use by the military or for collectors in countries and states where it is legal to do so.