As stated in Section 99, it is often desirable to pivot windows consisting of a single sash and especially those that are of an irregular shape. For windows of moderate size, pivoted at the sides, the sash centre shown in Fig. 410 may be used. Very heavy or large windows should be pivoted at the top and bottom, and for such windows the style of sash centre shown in Fig. 435 is preferable. This centre is made 4 and 5 inches long and inch thick, and should be of bronze metal that it may not rust.

Windows pivoted top and bottom should be provided with a sash adjuster (of which one pattern, the Yale, is shown in Fig. 436), that will hold the sash in any position. Sash adjusters also make the best trimming for a window pivoted at the sides, unless the window is so high that the adjuster cannot be readily reached, when a transom lifter may be used.

Fig. 437.   Parliament Butts.

Fig. 437. - Parliament Butts.

Fig. 438.   Surface Shutter Hiuge.

Fig. 438. - Surface Shutter Hiuge.

The Howarth Reversible Sash and Sash Centre Co., makes an automatic spring; sash centre that they claim will hold any sash in any desired position. The centres are made in different sizes, adapted to the smallest or the largest plate glass window and for either vertical or horizontal swing.

Fig. 439.   Three Cold Shutter Flap.

Fig. 439. - Three-Cold Shutter Flap.

Fig 440   Shutter Bar.

Fig 440 - Shutter Bar.