'locking device' is correct and usable in written English.
You can use it to refer to any kind of mechanism used to prevent unauthorized access to something. For example, "The laptop was protected by a secure locking device."
C. J. Chivers (NYT) WHITE PLAINS: GUN BILL The Westchester County Legislature has passed a scaled-down gun safety bill that requires owners to keep a locking device on their guns or to keep their guns in a locked container.
Until the mid-nineteen-sixties, few of America's nuclear weapons contained a locking device.
At one end of the basin was a small sluice or spillway with a locking device.
Most modern handcuffs are made of steel, adjustable to the wrist size, and equipped with an automatic locking device.
"We have designed a locking device to keep it in an open position, and we have other means of egress," Mr. Riehm said.
The F.B.I. posted a photograph of the collar and its locking device on its Web site, www.fbi.gov, and opened a hot line for tips, (866) 219-200866
* * * The Kennedy Administration soon decided to put locking devices inside NATO's nuclear weapons.
The Kennedy Administration soon decided to put locking devices inside NATO's nuclear weapons.
Global positioning systems and coded locking devices have helped many owners track and retrieve their stolen cars.
The first phase, which sought to "improve airplane security … immediately" included steel bars and locking devices installed on doors.
The airline is now putting extra locking devices on seats on 49 of its 767s used on international flights, and that work will be completed next weekend.
