John Willie

A post, waist high, driven in the ground or firmly secured to the floor. A captive is tied to it at wrists, knees and ankles, frequently for a whipping.

Named in honor of John Alexander Kouts, aka John Willie, English author / illustrator of Bizarre magazine. One of his most famous watercolors shows a woman tied to such a post.

John Willie is also a euphemism for an erect penis, which this sort of post suggests.