There are a number of jokes like this which I adore; for example; an old-fashioned slave manned galleon is so big that the slaves rowing down one end can't keep time with the slaves down the other. The galley master invests in a drum to keep time but the slaves at the bottom still can't hear so they decide to move the drum into the middle of the ship where everyone can hear but ... the drum is huge ... how to do it? Eventually, after much cogitation (no, 'Spaw that is a perfectly legit word) they decide the easiest way to move it is by greasing the chests of the slaves, laying them side to side and rolling the drum along it and as they do so they sing ... We're rolling a gong on the chest of a slave