Male - Any part, such as a bolt, designed to fit into another (female) part. External threads are male.
Manufactured wood - A wood product such as a truss, beam, Glue Lam TM or joist which is manufactured out of smaller wood pieces and glued or mechanically fastened to form a larger piece. Often used to create a stronger member which may use less wood. See also Oriented Strand Board.
Manufacturer's specifications - The written installation and/or maintenance instructions which are developed by the manufacturer of a product and which may have to be followed in order to maintain the product warrantee.
Marginal cost - The cost of one additional unit of something, for example, the cost to find, pump, ship and deliver the next new gallon of oil.
Masonry - Brick, tile, stone, concrete units, etc., or combinations thereof, bonded with mortar. Something constructed using bricks or stones.
MBh - Thousands of Btu's per hour; a measure of the heating capacity of a heating system.
Millwork - Woodwork such as doors, sashes and trim that have been shaped, usually by a milling machine.
Miter - A joint formed by beveling the edges or ends of two pieces at 45-degree angles, then fitting them together to make a 90-degree angle.
Mortar - The bonding agent between bricks, blocks, or other masonry units. Consists of water, sand, and cement—but not gravel. Also see concrete.
Mortise - A hole, slot, groove, or other recess into which another element fits. Most hinges, for example, are mortised so they lie flush.
Muriatic acid - Commonly used as a brick cleaner after masonry work is completed.
NEC (National Electrical Code) - A set of rules governing safe wiring methods. Local codes—which are backed by law—may differ from the NEC in some ways.
Neutral wire - Usually color-coded white, this carries electricity from an outlet back to ground. Also see hot wire and ground.
Newel post - A post at the bottom, landing, or top of a staircase to which the handrail is secured.
No-hub - A clamp-and-sleeve system for joining together cast-iron drainage pipes. Older hub-type pipes had to be leaded at all joints.
Nozzle - The part of a heating system that sprays the fuel of fuel-air mixture into the combustion chamber.