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.
These are so named when the pins or dovetails, or both, are hidden from view in the finished article. One plan, in which the joint is seen at the side only, is shown in Fig. 515. The wood a forming the side should be rather thinner than b on the front. The pins c are cut first, and their outline is marked out on b, in which the sockets are then cut for their reception, noting that these sockets do not extend farther in length than the dotted line d, nor farther in width than the dotted line e.
The plan illustrated in Fig. 516 allows only a line to be seen in the side piece. In this case, each piece has a distance marked off on it equalling the thickness of the piece to be joined to it; at about half this thickness another line is marked to indicate the depth (in the thickness of the wood) to which the pins and dovetails are to be cut. As the pins in a have to overlap and hide the ends of the dovetails, half their (the pins') length is cut off after their full dimension has been used in marking out the dovetails. All the cutting must be carefully done with a chisel. When the joint is complete and dry, the edge of the lap on a can be rounded. Or again, by making a lap on each piece and cutting the edges of the laps to the same bevel, they will meet so as to exhibit only a single line at the corner.