=55. Bronze or Brass Knobs.=—Knobs of bronze or brass are always used in buildings of the better class, and all ornamental knobs of the higher grade are made of these materials. The best knobs are usually solid; that is, cast in one piece, with the exception that the shank is inserted. Others are made in composite form, consisting of a steel interior shell, or frame, over which is tightly drawn an external section, or covering, of wrought-bronze or brass of substantial thickness. The completed knob, if properly made in this manner, is practically as strong as the hollow-cast knob and resists bruising or other injury. =56. Glass Knobs.=—The most expensive knobs made are those of cut glass with metal mountings. Several knobs of this kind are illustrated in Fig. 62. Cut-glass or crystal-glass knobs are very costly, the price depending on the style and the amount of cutting required and on the grade of glass used. The new method of mounting glass knobs allows for adjusting the knobs to doors of varying thicknesses, and also gives the knobs a handsome appearance, making them both durable and reliable. =57. Styles and Sizes of Knobs.=—The pottery knobs, such as the mineral, jet, and porcelain knobs, are made only in spheroidal and oval shapes. The spheroidal knobs are 2¼ inches in diameter, and the oval knobs 2½ in. × 1¾ in. Cast-iron and stamped-steel knobs are made spheroidal and of the box pattern, with plain and molded edges, both styles of knobs being about 2¼ inches in diameter. Bronze and brass knobs are usually spheroidal or ball-shaped, and are 2¼ and 2½ inches in diameter. They are also made oval and egg-shaped, these latter styles being provided in two sizes, namely, 3 in. × 2 in. and 2½ in. × 1¾ in. The same general dimensions obtain for wooden and glass knobs. [Illustration: FIG. 62] =58. Lock Spindles.=—In supplying a pair of knobs, there is always included with them the _spindle_, which connects them and passes through the hub of the lock. The type of spindle generally used is the =common=, or =side-screw=, =spindle=, which is shown in Fig. 63. In this spindle, the knobs are secured by means of a knob screw passing through a hole in the knob and engaging with one of the threaded holes in the spindle. There are several holes in the spindle, so that the distance the knobs are apart may be adjusted properly. Should further adjustment be required, it is accomplished by placing thin washers at the end of the knob shank. This type of spindle is generally used with the cheap grades of trim, and should not be used in high-grade work. [Illustration: FIG. 63]