Lath

A lath or slat is a thin, narrow strip of straight-grained wood used under roof shingles or tiles, on lath and plaster walls and ceilings to hold plaster, and in lattice and trellis work.

Lath has expanded to mean any type of backing material for plaster including a metal wire mesh or expanded metal that is applied to a wood or metal framework as matrix over which stucco or plaster is applied and wallboard products called gypsum or rock lath. Also reed mat was historically a lath material. One of the key elements of lath, whether wooden slats or wire mesh, are the openings or gaps that allow plaster or stucco to ooze behind and form a mechanical bond to the lath where gypsum lath relies more on a chemical bond.