This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
A piece of board, thickness not important, is cut off 17 in. long, and 8 1/2 in. deep; 2 strips (a, Fig. 615), 1 in. square, and 8 1/8in. long, are nailed across the ends exactly square, and with a space of 14 in. between. The ends of the strips are level with one edge of the board. Another 1-in. strip b is pivoted in the centre by a screw, the ends are rounded off, and the sides are held firmly while being nailed. Two nails are driven half-way in 15 1/2 in. apart, and serve to keep the top bar in its place while being nailed.