Using plaster skilfully is a craft worth learning. A poorly applied malleolar cast, for example, can make it impossible to reduce an ankle fracture. A really critical cast can mean so much to a patient that you should try to apply it yourself. Less critical casts can be applied by an assistant, but only provided you train him carefully and continually supervise him. Ways of making each particular cast are described later, so here are some of the points of technique which apply to all of them.