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.
In all cases the proper connection of the parts is an essential element, and in designing or executing joints and fastenings in woodwork, the following principles, laid down by Professor Rankine, should be adhered to, viz.: -
(1) To cut the joints and arrange the fastenings so as to weaken the pieces of timber that they connect as little as possible.
(2) To place each abutting surface in a joint as nearly as possible perpendicular to the pressure which it has to transmit.
(3) To proportion the area of each surface to the pressure which it has to bear, so that the timber may be safe against injury under the heaviest load which occurs in practice, and to form and fit every pair of such surfaces accurately in order to distribute the stress uniformly.
(4) To proportion the fastenings so that they may be of equal strength with the pieces which they connect.
(5) To place the fastenings in each piece of timber so that there shall be sufficient resistance to the giving way of the joint by the fastenings shearing or crushing their way through the timber.
(6) To these may be added a 6th principle not less important than the foregoing; viz. to select the simplest forms of joints, and to obtain the smallest possible number of abutments. The reason for this is that the more complicated the joint, or the greater the number of bearing surfaces, the less probability there will be of getting a sound and cheaply-made connection.