The Forgetful Captain's Socks

A pair of men's socks, sold by a ships chandlers. However the socks are not the same colour - one is green and one is red. The idea is to remind the forgetful captain which direction is port and which is starboard.

As Tim says, he remembers the old mnemonic - there is no more red port left, in other words port is left and the port light on a ship is the red one. Obviously starboard is green and right.

I guess the socks could help to remind you - so long as you remembered to put them on the right feet in the first place!