This article was updated May 5, 2023. It was originally published Sept. 24, 2009. Shaft keys—sometimes called sunk keys—transmit torque between shafts and shaft-mounted components such as gears or ...

Also called a "dongle," it is a software copy protection device that plugs into the USB port of the computer. Upon startup, the application looks for the key and will run only if the key contains the ...