steel trap

a trap for catching animals, consisting of spring-operated steel jaws with sharp projections that clamp shut.

Origin of steel trap

First recorded in 1725–35

I at least admire her audacity and her steel-trap quickness of mind.

The Prairie Child |Arthur Stringer
If they knowed as much as we servants, they'd as soon jam their fingers into a steel-trap.

Alone |Marion Harland
Among the crew was one they called Jamie, as smart as a steel-trap, and handsome as a picture.

The Atlantic Monthly, Vol. 13, No. 79, May, 1864 |Various
Stepping over, he unhooked it, and then it was an easy matter to pry the jaws of the steel-trap apart.

Dave Porter and the Runaways |Edward Stratemeyer

She's smarter'n a steel-trap, and might have been a lawyer herself.

Harper's Young People, May 18, 1880 |Various