In this video Paul Sellers shows how to make a simple shooting board from pine. This is an important piece of equipment for woodworking in the hand tool shop as it allows you to make sure the end of a board is either exactly square or exactly forty-five degrees. It also allows you to plane the end of a board straight across without 'break-out' on the far side.
At 1:47 the middle measurement should be 12 1/2" or 320mm. Sorry for the confusion.