[f. LAG v.4 + -ING1.] The action of the vb. LAG4.
1. The action of covering a boiler, an arch, a wall, etc., with strips of wood or felt.
1870. Eng. Mech., 11 Feb., 516/1. This may be … prevented by careful ‘lagging’ with non-conductors of heat.
1895. Hatch & Chalmers, Gold Mines of Rand, vi. 121. Side lagging is seldom necessary after the first 50 or 100 feet.
attrib. 1884. Leisure Hour, Sept., 531/2. The old engine-house was exchanged for part of the old lagging-shop.
2. pl. and collect. sing. The material with which this is done. Also attrib.
1851. Pract. Mech. Jrnl., III. 242. The boiler is covered with lagging and Russia sheet iron.
1867. ‘Ben Brierley,’ Marlocks Merriton, 68. The fence (his own making) was but a rickety fabric of ‘laggins,’ worn-out treadles [etc.].
1869. Lonsdale Gloss., Laggins, the part of the wooden frame work upon which the stones are laid when building an arch.
1870. Spon’s Dict. Engineering, II. 479. The term bolster has also been applied to the pieces of timber placed across the rībs of the centering of an arch to support the voussoirs; but these are more generally known by the name of laggings.
1881. Raymond, Mining Gloss., Lagging, planks, slabs, or small timber placed over the caps or behind the posts of the timbering.
