In the following paragraphs, the meanings of various technical terms frequently used in stone masonry, are clearly explained:

Arris - The external edge formed by two surfaces, whether plane or curved, meeting each other.

Ashlar - A stone wall built of stones having rectangular faces and with joints dressed so closely that "the distance between the general planes of the surfaces of the adjoining stones is one-half inch or less."

Ax or Pean Hammer - This tool (Fig. 20) is similar to a double-blacled wood-ax. It is used after the stone is rough-pointed, to make drafts along the edges of the stone. For rubble work, and even for squared-stone work, no finer tool need be used.

Backing - The masonry on the back side of a wall; usually of rougher quality than that on the face.

Batter - The variation from the perpendicular, of a wall surface. It is usually expressed as the ratio of the horizontal distance to the vertical height. For example, a batter of 1:12 means that the wall has a slope of one inch horizontally to each twelve inches of height.

Bearing Block - A block of stone set in a wall with the special purpose of forming a bearing for a concentrated load (such as the load of a beam).

Bed-Joint - A horizontal joint, or one which is nearly perpendicular to the resultant line of pressure (see Joint).

Fig. 20. Ax or Pean Hammer.

Fig. 20. Ax or Pean Hammer.

Belt-Course - A horizontal course of stone extending around one or more faces of a building; it is usually composed of larger stones which sometimes project slightly, and is usually employed only for architectural effect.

Bonding - A system of arranging the stones so that they are mutually tied together by the overlapping of joints.

Bush-Hammering - A method of finishing by which the surface of the stone, after being roughly dressed to a surface which is nearly plane, is smoothed still more with a bush-hammer (see Fig. 21). The face of the bush-hammer has a large number of small pyramidal points, which, in skilful hands, speedily reduce the surface to a uniformly granular condition.

Fig. 21. Bush Hammer.

Fig. 21. Bush-Hammer.

Fig. 23. Cavil.

Fig. 23. Cavil.

Fig. 22. Buttress.

Fig. 22. Buttress.

Fig. 24. Chisel.

Fig. 24. Chisel.

Buttress - A very short wall (Fig. 22) built perpendicular to a main wall which may be subjected to lateral thrust, in order to resist by compression the tendency to tip over. (See Counterfort.)

Cavil - A tool which has one blunt face, and a pyramidal point at the other end (Fig. 23). It is used for roughly breaking up stone.

Chisel - A tool made of a steel bar which has one end forged and ground to a chisel edge (Fig. 24). It is used for cutting drafts for the edges of stones.

Coping - A course of stone which caps the top of a wall.

Corbel - A stone projecting from the face of a wall for the purpose of supporting a beam or an arch which extends out from the wall.

Counterfort - A short wall built behind a retaining wall, to relieve by tension the overturning thrust against the wall. (See Buttress.)

Course - A row of stones of equal height laid horizontally along a wall.

Coursed Masonry - Masonry having courses of equal height throughout.

Coursed Rubble - Rubble masonry (see Rubble) which is leveled off at certain definite heights so as to make continuous horizontal joints. The expediency of this is doubtful. It certainly adds something to the cost; it probably makes the wall somewhat weaker, and is no advantage either mechanically or in appearance.

Cramp - A bar of iron, the ends of which are bent at right angles, which is inserted in holes and grooves specially cut for it in adjacent stones in order to bind the stones together. When they are carefully packed with cement mortar, they are effectively prevented from rusting.

Crandall - A tool made by fitting a series of steel points into a handle, using a wedge (see Fig. 25), by means of which a series of fine picks at the stone are made with each stroke, and the surface is more quickly reduced to a true plane.

Crandalling - A system of dressing stone by which the surface, after having been rough-pointed to a fairly plane surface, is hammered with a crandall such as is illustrated in Fig. 25.

Dimension Stone - Cut stone whose precise dimensions in a building are specified in the plans. The term refers to the highest grade of ashlar work.

Dowel - A straight bar of iron, copper, or even stone, which is inserted in two corresponding holes in adjacent stones. They may be vertical across horizontal joints, or horizontal across vertical joints. In the latter case, they are frequently used to tie the stones of a coping or cornice. The extra space between the dowels and the stones should be filled with melted lead, sulphur, or cement grout.

Draft - A line on the surface of a stone which is cut to the breadth of the draft chisel.

Fig. 25. Crandall.

Fig. 25. Crandall.

Dry Stone Masonry - Masonry which is put in place without mortar.

Extrados - The upper surface of an arch.

Face - The exposed surface of a wall.

Face-Hammer - A tool having a hammer face and an ax face. It is used for roughly squaring up stones, either for rubble work or in preparation for finer stone dressing. See Fig. 26.

Feathers - See Plugs.

Footing - The foundation masonry for a wall or pier, usually composed (in stone masonry) of large stones having a sufficient area so that the pressure upon the subsoil shall not exceed a safe limit, and having sufficient transverse strength to distribute the pressure uniformly over the subsoil.