A switchblade knife was a type of knife whose blade could be concealed by pressing a switch.
In 2004, a switchblade knife was stashed in Loomis' automobile, a Chevrolet Caprice. The knife was kept in the crevice where the back cushion of the passenger seat met the actual seat. While kidnapped by Jonathan Archer and T'Pol in 2004 but momentarily sitting alone in the car, Loomis secretly pulled the knife out of its hiding place and activated the blade before returning the knife to the back of the seat. Loomis later swung the knife at T'Pol and they fought over the weapon, though T'Pol eventually managed to stun Loomis with her phase-pistol. (ENT: "Carpenter Street")