KEY COURSE. 1. A horizontal row of keystones passing through the center of an arch. Generally used because the archway is too deep for a single keystone (or a single transverse row of arch stones) to suffice. 2. A course of keystones used in the crown of a barrel vault.
KEYSTONE. Wedge-shaped stone at the center of an arch or vault.
KILN. A furnace oven or heated enclosure used for burning or firing brick or other clay material.
Kiln Run. Brick from one kiln which have not been sorted or graded for size of color variation
KING CLOSER. A closer to fill an opening in a course, usually three-fourths the size of a regular brick.
KNEELER. A building stone shaped to change a direction of the masonry.




Premanufactured reinforcement. Side wires are connected in a single plane by perpendicular cross wires.
LAP. The distance one masonry unit or reinforcing extends over another.
LATERAL SUPPORT. Means whereby walls are braced either vertically or horizontally by columns, pilasters, cross walls, beams, floors, roofs, etc.
LAYING TO BOND. Laying the brick of the entire course without using a cut brick.
LEAD. The section of a wall built up and racked back on successive courses. A line is attached to lead as a guide for constructing a wall between them.
LEWIS. Any of several metal devices for lifting stone blocks in the quarry or mill or for hoisting columns or other heavy masonry units in construction.
Box Lewis. An assembly of metal components, some or all of which are tapered upward, that is inserted into a downward-flaring hole (dovetail mortise) and cut into the tops of columns or other heavy masonry units for hoisting.
LIME. A critical ingredient of masonry mortars and grouts.
Hydrated Lime. Quicklime to which sufficient water has been added to satisfy its chemical affinity and convert the oxides to hydroxides.
Lime Putty. Hydrated lime in plastic form ready for addition to mortar.
Quicklime. A hot, unslaked lime. A calcined material, a major part of which is calcium oxide (or calcium oxide in natural association with lesser amounts of magnesium oxide) capable of slaking with water.
Slaked Lime. Formed when quickline is treated with water; same as hydrated lime.
Rock of sedimentary origin composed principally of calcite or dolomite or both.
LINE. The string stretched taut from lead to lead as a guide for laying the top edge of a brick course.
Line Pin. A metal pin used to attach line used for alignment of masonry units.
LINER. In the fabrication of stone veneer (principally marble), the stone bonded to the back of thin sheets to add strength, rigidity, bearing surface, or depth of joint.
LINING. A wythe of similar masonry that is bonded to an existing wall to reinforce it.
LINTEL. A structural member placed over an opening or a recess in a wall and supporting construction above. Lintel may be of steel, precast concrete, reinforced masonry constrution. (UBC)
LUG. A projection from, or extension of, a building unit that engages an adjacent unit; for example, that part of a sill that extends into an adjoining jamb.
LUG SILL. A sill that projects into the jambs of a window or door opening.
LISTED or LISTING. Terms referring to equipment and/or materials which are shown in a list published by an approved testing agency, qualified and equipped for experimental testing and maintaining an adequate periodic inspection of current productions and whose listing states that the equipment and/or material complies with recognized safety standards.




Masonry Institute of Washington.
A short-handled wooden hammer, with a truncated conical head, used to work stone and to drive mallet-head shaping tools.
MARBLE. 1. A metamorphic rock made up largely of calcite or dolomite. 2. A rock that will polish and that is composed mainly of calcite or dolomite or, rarely, serpentine.
Artificial Marble. Precast terrazzo.
MASH HAMMER. A short-handled heavy hammer, with two round or octagonal faces, used to drive hammer-head shaping tools.
MASONRY. That form of construction composed of stone, brick, concrete, gypsum, hollow clay tile, concrete block or tile or other similar building units or materials or combination of these materials laid up unit by unit.
Masonry Cement. A mill-mixed cementitious material to which sand and water must be added. ASTM C91.
Masonry Chimney. A chimney of masonry units, bricks, stones or masonry chimney units.
Plain Masonry. Masonry constructed without steel reinforcement, except that which may be used for bonding or reducing the effects of dimensional changes due to variations in moisture content or temperature.
Reinforced Masonry. Masonry constructed with steel reinforcement embedded in such a manner that the two materials act together in resisting forces.
Solid Masonry. Masonry of solid units built without hollow spaces.
MASONRY UNIT. Natural or manufactured building units of burned clay, concrete, stone, glass, and gypsum.
Height. The vertical dimension of the unit in the face of a wall. ASTM C43.
Length. The horizontal dimension of the unit in the face of the wall. ASTM C43.
Nominal Dimension. A dimension that may be greater than the specified masonry dimension by the thickness of a mortar joint. ASTM C43.
Shells. The outer walls. ASTM C43.
Exposed Finished. Units whose surfaces are intended to be left exposed or painted. ASTM C43.
Natural Finished. Units having unglazed or uncoated surfaces burned to the natural color of the material used in forming the body. ASTM C43.
Non-Lustrous Glazed. Units whose surface faces are covered by an inseparable fire-bonded ceramic glaze of non-lustrous finish. ASTM C43.
Opaque Ceramic Glazed. Units whose surface faces are covered by an inseperable fire-bonded, opaque, colored ceramic glaze of bright stain or gloss finish. ASTM C43.
Plaster-Base Finished. Units whose surfaces are intended for the direct application of plaster. ASTM C43. (Note: Plaster-base finish units may be smooth, scored, combed or roughened.)
Roughened Finished. Units whose plane die surfaces are entirely broken by mechanical means, such as wire cutting or wire brushing. ASTM C43.
Salt Glazed. Units whose surface faces have a lustrous glazed finish from the thermochemical rection of the silicates of the clay body with vapors of salt or chemicals. ASTM C43.
Sand Finished. Units whose suface faces are covered with sand, applied either to the clay column in the stiff mud process or as the lubricant to the molds in the soft mud process. ASTM C43.
Scored Finished. Units whose face surfaces are grooved as they come from the die. ASTM C43.
Hollow Masonry Unit. One whose net cross-sectional area in any plane parallel to the bearing surface is less than 75 percent of the gross.
Modular Masonry Unit. One whose nominal dimensions are based on the 4-in. module.
Solid Masonry Unit. One whose net cross-sectional area in every plane parallel to the bearing surface is 75 percent or more of the gross.
MASON'S SCAFFOLD. Besides being totally self supporting, the true mason's scaffold must also carry the load of the masonry materials. It may be braced on a bridging already erected.
MORTAR. A plastic mixture of cementitious materials, fine aggregate and water. See ASTM Specifications C270, C476.
Fat Mortar. Mortar containing a high percentage of cementitious components.
High-Bond Mortar. Mortar which develops higher bond strengths with masonry units than normally developed with conventional mortar.
Lean Mortar. Mortar which is deficient in cementitious components.

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