Дополнение к ответу на вопрос Shaman`a:После 1945 года американские солдаты, вернувшиеся из Европы, привезли предметы, известные как "Итальянские стилеты с выбрасывающимся лезвием". Именно эта формулировка потом стала общей для названия ножей такого типа.(After 1945, American soldiers returning home from Europe brought along individually purchased examples of what would become known as the Italian stiletto switchblade. Consumer demand for more of these knives resulted in the importation of large numbers of side-opening and telescoping blade switchblades, primarily from Italy. These imported switchblades were frequently referred to as stilettos, since most incorporated a long, slender blade tapering to a needle-like point, together with a slim-profile handle and vestigial cross-guard reminiscent of the medieval weapon).К реплике servy:Американский акт о ножах с выбрасывающимся лезвием запрещает любой оборот (в том числе и ношение) таких ножей по единственному признаку – выбрасывающемуся лезвию. Аналогичные законы приняты во многих странах, в т.ч. в Великобритании.(The Switchblade Knife Act, (Pub.L. 85-623, 72 Stat. 562, enacted on August 12, 1958, and codified in 15 U.S.C. §§ 1241–1245), prohibits the manufacture, importation, distribution, transportation, and sale of switchblade knives in commercial transactions substantially affecting interstate commerce[54] between any state, territory, possession of the United States, or the District of Columbia, and any place outside that state, territory, U.S. possession, or the District of Columbia. The Act also prohibits possession of such knives on federal or Indian lands or on lands subject to federal jurisdiction. It does not prohibit the ownership or carrying of automatic knives or switchblades inside a state while not on federal property, nor does it prohibit the acquisition or disposition of such knives in an intrastate transaction or an interstate transaction that is noncommercial and/or does not substantially affect interstate commerce (as defined by recent decisions of the U.S. Supreme Court).U.S. Code Title 15, Sect. 1241 defines switchblade knives as any knives which open "1) by hand pressure applied to a button or other device in the handle of the knife, or any knife having a blade which opens automatically; by operation of inertia, gravity, or both".)Материалов на эту тему много, я ссылаюсь на лежащие на поверхности – из англоязычной Википедии.