The frame housing the wax comb uses a long bar along its top edge which projects beyond the boundary of the frame. Each end of the bar rests on a parallel ledge, one on each side of the nest cavity. It is the length of this projection (the bar end or 'lug') that is said to be 'short' or 'long'. Long lugs are often considered to be easier to pick up with your fingers, but also tend to break off more frequently, than short lugs. In addition, as honey bees may fix the lugs to the ledge with propolis, a longer lug becomes more securely fixed that a short one, increasing the chance of it breaking as it is levered out. As a consequence of this where long lugs are used a thin strip of plastic or tin is fixed to each ledge to raise the lug above the surface of the ledge a fraction so that it is less readily attached. This has to be done with care so as not to interfere with the bee space, and it usually results in an increased amount of propolis around the lugs. Short lugs, designed to sit on a slimmer ledge, are simpler and cheaper for equipment makers to produce, and have the advantage that their potential for squashing bees when a frame is placed back on the ledge is reduced because of their smaller surface area.