Concertina-action double-top tables
Figure 381 shows the side elevation with double top and end-fixing card-table hinges. In 381:2 the back legs (hinged side of top) are not
connected to the table frame, but to hinged rails extending as 381:2 and closing up as 381:3. Figure 381:2A shows a special top-fixing hinge often used in old examples, but back flap or piano hinges can be used. The frame when opened is kept rigid by a sliding shelf pulled along the grooves worked in the rails (381:4), and the top is then folded over. Figure 381:5 shows an improved version more rigid in performance, in which stub rails (381:5A) are barefaced tenoned into the legs and a show rail (381:5B) tenoned and glued to the front leg and glued to the adjoining stub rail, and tenoned but not glued to the other leg. The stub rails are knuckle jointed to the hinged rails, which are also knuckle jointed at 381:5C with extra long shoulder bevels to allow the joint to close at the acute angle (381:5D). A cabin hook and eye can be fitted to keep the frame rigid in the open position, as a groove for a slide (381:4) cannot be worked across the knuckle without seriously weakening the joint. The method usually adopted for keeping the back legs in the closed position was to recess a 3/16 in (5 mm) wood spring into the underside of the top, with a projecting, knob which clipped over the rail as shown in the drawing (382).