Arrow

push the wrench sideways, and the bolt moves up or down.

a wrench on a bolt: push across the handle and the bolt screws in or out of the plate; push along it and nothing turns

A wrench turns a bolt by torque, r × F: the handle r, your push F, and the sine of the angle between them. Push straight across the handle and it turns hardest; push along it and sin θ is zero, so nothing turns. The torque points along the bolt, out of the plane both arrows lie in, and a right-hand thread moves the bolt that way: clockwise drives it in, anticlockwise brings it out.

Concepts: geometry, trigonometry.

An interactive you play with one thumb, on Wundr.