Chris Green wrote:

Dave Plowman wrote:

How does the spindle lock work on a drill? The type that lets you use a
keyless chuck one handed? More specifically, how does it disengage when
you switch on?

On drills with a keyless chuck it's a type of gear[ing] that only
works when transmitting power in one direction. I guess it's a bit
like a ratchet except that it works on both directions. There's a
specific name for it which I'm afraid I can't remember. :-)

A sprag clutch?