(a) Photograph of the jig standing on its base assembly. (b) Photograph of detached plate-holder assembly. (c) Photograph showing the pendulum beam stop assembly mounted on the Rigaku 944 CCD detector. The chassis, a, is made from plastic trunking, which accommodates a plastic pivot, b, from which the pendulum is hung. The pendulum is assembled from a strip of A4 overhead projector acetate, c, and an 8 mm steel disc, d.