The joints by which the outer tympan is attached to the carriage, on which it works. They are riveted to the bottom end of the tympan by one of the sides, and the other side has an upright notch cut in it: at the back of the hind part of the coffin are fixed two projecting screws, at the same distance from each other as the notches in the joints; these screws have a square plate or washer on each of them, and a flat-headed female screw; the tympan joints are slipped over these screws by the notches, so that they bestride each screw, and are confined by the female screw and washer. The tympan can thus be adjusted to any height, by loosening the screws and sliding the joints up or down. The pin that connects the two parts of the joints is stout, and made to slip out when necessary. These joints should be particularly well made, and have no play; if they have, it will cause maculing and doubles in the work.