Corbel:  a projection of stone or timber jutting out from a wall to support a weight.
Boss:  A piece of ornamental carving covering the point where the ribs in a vault or ceiling cross.

The ceiling of the Nave has some carved wooden bosses, whilst at the line where it meets the walls are some amusing corbels.  They are very high up and difficult to photograph - when using a high zoom a slight shake of the hand shows as a big movement;  secondly the corbels are near lights and windows so they appear to be dark in comparison.  However, St. Mary's has some great corbels and bosses, so we have included them here to give you a 'feel' of them even though the detail on the photograph isn't good.