knife switch

from the GNU version of the Collaborative International Dictionary of English.

• (Elec.) A switch consisting of one or more knifelike pieces hinged at one end and making contact near the other with flat gripping springs.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A switch used to control the flow of electricity in a circuit, consisting of a hinge which allows a metal lever, or knife, to be lifted from or inserted into a slot or jaw.