This section is from the book "The Building Trades Pocketbook", by International Correspondence Schools. Also available from Amazon: Building Trades Pocketbook: a Handy Manual of reference on Building Construction.
A bevel-shoulder joint (a), Fig. 5, is a mortise and tenon used to unite inclined to upright or horizontal pieces. It is made by cutting beveled shoulders on the inclined piece and a corresponding sinking in the cheeks of the mortise of a post or beam.
A bird's mouth joint (b) is an angular notch cut in a timber to allow it to fit snugly over the piece on which it rests.
A bridle joint (c) is one in which the mortise is supplanted by a tongued notch and the tenon by a grooved socket. The tongue, called the bridle, is equal to about one-third the thickness of the timber.
A cogged joint (d), called also a corked joint, is made with
Fig. 5. (a)
Fig. 5. (6) a cog in the top of the lower timber, and a corresponding notch in the under surface of the upper timber.
The cottered joint (e) is used in tightening up tie-beams to king posts, etc, and consists of a steel strap and slip wedges.
In a notched joint (f), made by cutting a notch in each piece of timber, the notches are always less in depth than one-half the thickness of the material.
The dovetail joint (g), used to obtain a close, rigid union, consists of a wedged-like pin cut in the end of one piece, and a corresponding notch in the other.
A fished joint (h), used for joining timbers in the direction of their length, is formed by butting the squared ends together and placing short pieces of wood or iron, called fishplates, over the faces of the timbers and bolting or spiking the whole firmly together.
The fox-wedged joint (i) is used to secure the tenon in a mortise that is not cut through. Thin wedges of hard wood are placed in saw cuts in the end of the tenon. On driving in the tenon the wedges cause it to expand and fit tightly in the mortise, which is dovetailed or widened out at the back.
A halved joint (j) is made by notching each piece one-half of its thickness, so that the top and bottom surfaces of both timbers are flush. Beveled or dovetailed halving is shown at (k).
The scarf joint (I) is used where the timber has to be lengthened; this joint forms a rigid splice.
A lap joint (m) is made by laying one end of a timber over another and fastening them together with bent straps, which have screw ends by which they may be tightened. The efficiency of this joint can be increased by inserting hardwood tongues across the faces in contact.
The lip joint (n) is furnished with a lip a to make a stronger cross-section. It may also be applied to halved or dovetailed joints.
A tusk-tenon joint (o) is formed by inserting a tenon into a corresponding mortise. The tenon is strengthened by a shoulder at the root called a tusk. The tenon is generally one-sixth the thickness of the timber, and is placed midway in the depth. The upper shoulder is beveled so as to avoid cutting away the material of beam into which it is inserted. This joint is a common one for uniting tail-beams to headers in floor framing.
A checked joint (p) is made when two pieces cross each other, and it is desired to reduce the height occupied by the upper timber.
The socket joint (q) is formed by inserting the ends of timbers into an iron casting. It is commonly used at the apex and toes of principal rafters. When used for the latter purpose, provision must be made to permit the evaporation of the sap.
The strap joint, shown in elevation and plan at (r) and (s), is made by girding the joint by a strong iron band. This joint is an approved method of tying the foot of a principal rafter to a tie-beam composed of two planks.
The tie joint (t) is one usually adopted to tie the inclined rafter to the tie-beam, and prevent it from spreading.