[Illustration: FIG. 27.--Croydon Central Library. Open Access Lending Department, showing Double Wickets (Section 133).] =135.= Sometimes a simple barrier is required in some kinds of reference libraries to separate bookcases from reading rooms. This may be either fixed or movable, and a good form can be constructed of ornamental ironwork, surmounted by a polished oak or walnut rail, about four to six inches wide, in the style of illustration (Fig. 30). [Illustration: FIG. 28.--Triple Open-Access Barrier (Section 133).] =136. Screens.=--In small libraries with a small staff it is often possible to obtain complete oversight of nearly every department by using glazed partitions or screens instead of opaque internal walls. In cases where there is no roof weight to be supported this is a very good arrangement, and is recommended for every building to which it can be applied. When such partitions separate rooms, it is advisable to carry them right up to the ceiling to exclude noise. In other situations, as when dividing a room into two or more sections, the screens need not be more than eight or nine feet high. Clear glass should be used throughout, unless in the upper panels, for the sake of both oversight and light. [Illustration: FIG. 29.--Treadle Latch for Open Access Wicket (Section 133).] [Illustration: FIG. 30.--Barrier for Dividing Rooms (Section 135).] =137. Lifts.=--In large libraries with many floors, passenger or other lifts for carrying heavy weights are desirable. In a building with two or more floors, an ordinary lift for transporting parcels of books to the extent of perhaps two hundredweights should be provided in a convenient place, preferably against a wall. Such lifts should have automatic brakes and simple raising and lowering mechanism; but an electric motor will be found less noisy and easier to work than any form of rope lift. In addition, it is often of greater service to have small, quick-running lifts or tubes capable of carrying one to six single books from floor to floor. In cases where lending library books are issued for reading in the reading room, this is a very convenient arrangement, and it also greatly facilitates the work of the staff by enabling messages and small articles to be rapidly transferred from place to place.