Masonry - Stone, brick, concrete, hollow-tile, concrete block, gypsum block, or other similar building units or materials or a combination of the same, bonded together with mortar to form a wall, pier, buttress, or similar mass.

Mastic - A pasty material used as a cement (as for setting tile) or a protective coating (as for thermal insulation or waterproofing)

Metal Lath - Sheets of metal that are slit and drawn out to form openings. Used as a plaster base for walls and ceilings and as reinforcing over other forms of plaster base.

Millwork - Generally all building materials made of finished wood and manufactured in millwork plants and planing mills are included under the term "millwork." It includes such items as inside and outside doors, window and doorframes, blinds, porchwork, mantels, panelwork, stairways, moldings, and interior trim. It normally does not include flooring, ceiling, or siding.

Miter Joint - The joint of two pieces at an angle that bisects the joining angle. For example, the miter joint at the side and head casing at a door opening is made at a 45° angle.

Moisture Content of Wood - Weight of the water contained in the wood, usually expressed as a percentage of the weight of the ovendry wood.

Molding - A wood strip having a coned or projecting surface used for decorative purposes.

Mortise - A slot cut into a board, plank, or timber, usually edgewise, to receive tenon of another board, plank, or timber to form a joint.

Mullion - A vertical bar or divider in the frame between windows, doors, or other openings.

Muntin - A small member which divides the glass or openings of sash or doors.