AUTOMATIC-KNIVES also known as, pushbutton knife, ejector knife, spring knife (Sprenger,Springer , flick knife, or flick blade) is a type of knife with a sliding blade contained in the handle which is extended 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 blade is extended to the fully opened position. It is unlocked by a mechanism that allows the blade to be folded and locked in the closed position.
During the 1950s, US newspapers as well as the tabloid press promoted the image of a new violent crime wave caused by young male delinquents with a stiletto, switchblade, or flick knife, based mostly on anecdotal evidence. In 1954, Democratic Rep. James J. Delaney of New York authored the first bill submitted to the U.S. Congress banning the manufacture and sale of switchblades, beginning a wave of legal restrictions worldwide and a consequent decline in their popularity
The knife blade (dark grey) is locked in position by a spring-loaded restraining pin (yellow and red) fitting into a notch in the blade at position 1. The two spring carriers (green) fit into the spaces on the slide (blue) and this assembly rests to the side of the blade. The right spring carrier is restrained by a tab at position 2 that fits over the end of the blade. Tension on the main spring (red zig-zag) holds the other spring carrier, slide and thumb stud (light grey) to the right.