[Riley]

Good thing that I was never a pirate. With my warped sense of humor, I'd have the dreaded plank rigged as a powerful springboard. The poor victim gingerly edges out onto the thing, and WHANNNGGG!! He's flung over the rigging, dropping into the sea a hundred feet off of the other side of the ship.

[AnAmericanMother]

Sort of keel-hauling in reverse, huh?

I seem to recall something similar in a Conan Doyle story (not one of the Sherlock Holmes ones) of a trap rigged to fling the unwary through the air . . .