This section is from the book "A Practical Treatise On The Joints Made And Used By Builders", by Wyvill J. Christy. Also available from Amazon: Practical treatise on the joints made and used by builders.
Coursing Joint is the same as described in the Bricklayers' Section.
Cramp or Cramped Joint occurs in masonry when two blocks are locked together with a metal or slate cramp. If of metal, it should preferably be of copper or bronze rather than of iron, and cast or galvanised iron rather than wrought. A metal cramp consists of a bar with turned-down jagged ends, or else of double dovetail form, in the latter case sometimes 15 in. or 18 in. long, 4 in. broad, and 1 in. thick, fitting into a groove just large enough to admit of its being enveloped in Portland cement, sulphur, or lead, and left flush. Plaster of Paris is used for securing cramps in interior ornamental marble work. Slate cramps are cut to fit tightly, or they may be run like the others. The main difference nowadays between cramps and dowels in masonry may be said to consist in the former being always let in on the top surface of two stones of the same course, to hold them tight at the joint and not at the beds. Chimney pieces and other marble work are put together with small copper cramps. Small iron cramps made out of ¼ in. galvanised iron wire are likewise used. There is always a risk attending the use of iron cramps in stonework, both as regards stains and dislocations, as noticed under Run Joint, no matter how well protected from oxidation they may be, for some unforeseen contingency may abrade or displace part of their protective coating; yet at the same time if the exclusion of air is perfect there can be no corrosion. With any system of metal cramps whatever a good lightning conductor is imperatively necessary, owing to its determining instead of the cramps the polarisation of the electric fluid just previous to a discharge. Chain bars, mentioned under Collar Joint in the Smiths' Section, may be viewed as expanded cramps, the bars being furnished with stubs corresponding to the fangs or corkings of a cramp.
A transverse as opposed to a longitudinal joint. In ashlar the term "side joints" is more usual than cross joints, but the single word "joints" signifies, and is almost always used to signify, those surfaces of the blocks which form the cross joints. Face, back, beds, and joints comprise the six surfaces of an ashlar.
Dovetail Joint occurs in masonry when part of one stone is cut in the form of a reversed wedge to let into a sinking in another stone cut to receive it. Or it may be only cut as headers in ashlar facing are, viz., wider at the tail and for better bonding with the backing. In dovetailing together blocks in a course of ashlar, it is usual to sink the sides of the blocks so that the space between any two may form the expanding and contracting hole for a similarly fashioned block to fit into. Hence the transverse joints run in a zigzag direction as shown in Fig. 13, instead of taking the usual rectangular course, and in a similar manner the courses may be dovetailed together as well as the blocks.