Magnetic Catch A cupboard catch that uses a magnetised strike to hold the door closed.

Malleable A term used to describe metals that can be hammered, pounded or pressed into various shapes.

Maison Key System A keying system where a group of different keys will operate a common lock.

Master Key A key which will operate a group of locks, where each lock is generally keyed to differ.

Master Key System A system where locks are passed by two levels of keys. The lower level of key (keyed to differ) fits only that lock or those locks keyed alike. The higher level (master key) fits all locks in the system.

Meeting Stile The vertical edge of a door or window, in a pair, which is adjacent to the other door or window.

Metallurgy The science or technology of metals.

Mortice An opening, recess or cutout made to receive a lock or other hardware. Also the act of making such an opening.

Mortice Lock A lock designed to be inserted into the edge of a door, rather than being mounted to its surface.

Mould A form into which molten metal is poured to produce a casting.

Moulding Strips used for ornamentation.

Mullion A fixed or movable vertical member dividing a door opening.

Muntin The small members that divide the glass in a window frame.

Mushroom Pins A mushroom shaped pin used in a pin tumbler mechanism to increase pick resistance.