The thin metallic side plate of the handle of a pocketknife.
See Illust. of Pocketknife.

An incrustation deposit on the inside of a vessel in which
water is heated, as a steam boiler.

Hence, any layer or leaf of metal or other material,
resembling in size and thinness the scale of a fish; as, a scale of
iron, of bone, etc.

A small appendage like a rudimentary leaf, resembling the
scales of a fish in form, and often in arrangement; as, the scale of a
bud, of a pine cone, and the like. The name is also given to the chaff
on the stems of ferns.

One of the small scalelike structures covering parts of some
invertebrates, as those on the wings of Lepidoptera and on the body of
Thysanura; the elytra of certain annelids. See Lepidoptera.

One of the small, thin, membranous, bony or horny pieces
which form the covering of many fishes and reptiles, and some mammals,
belonging to the dermal part of the skeleton, or dermoskeleton. See
Cycloid, Ctenoid, and Ganoid.

The sign or constellation Libra.

The dish of a balance; hence, the balance itself; an
instrument or machine for weighing; as, to turn the scale; – chiefly
used in the plural when applied to the whole instrument or apparatus
for weighing. Also used figuratively.

To weigh or measure according to a scale; to measure;
also, to grade or vary according to a scale or system.

A scale insect. (See below.)