 Also, multiple knives may be attached to a single handle and can be used to activate more than one circuit simultaneously.Though used commonly in the past, knife switches are now rare, finding use largely in science experiments where the position of the switch may be plainly seen in demonstration.The knife switch is extremely simple in construction and use, but its exposed metal parts present a great risk of electric shock, and the switch is subject to arcing when opened at higher voltages, which poses a further risk of shock or burns to the operator and can cause fires or explosions under certain conditions.