50. See figs 17 and 18 of Plate III. It seems that the screw has a shaped tenon that slides into a dovetail - - queue d’aronde - cut in the long piece.

The rather charming French name queue d’aronde ‘swallow tail’ reminds us of the old name arondelle of the bird now called hirondelle , – as, for example, in the Rue de l’arondelle of the old Quartier Latin in which the famous surgeon Ambroise Paré had his house in the mid sixteenth century.