=286.= The most used and oldest of the British sheaf catalogues is the “Adjustable Catalogue-Holder,” which was invented about 1892. This has a flexible leather back, and the slips are bound and unbound by the contracting and expanding action of two cylindrical screws, turned by means of a metal key. It is not necessary, as in the case of all other sheaf-holders, to undo this one in order to remove the slips when additions are being made, the loosening of the screws being all that is necessary. The slips are punched at the back edge with bayonet-shaped or keyed slots, which give sufficient holding power when the screws are tightened to clamp the boards and slips into one solid and firm volume. The book numbers, if written on the clamped portion of the slips, will remain in the sheaf if entries should be wilfully torn out, and no catalogue could be rendered imperfect without the knowledge of the librarian. Xylonite label-holders are attached to the back of this form of sheaf, which enable contents labels to be changed at will, without pasting or damaging the back. A rack or pigeon-holes can be provided in which to store these sheafs in numbered, alphabetical or class order. [Illustration: FIG. 107.--Adjustable Sheaf Catalogue, Open for Consultation (Section 287).] [Illustration: FIG. 108.--Adjustable Sheaf Catalogue, Open for making Additions with Cradle and Key (Section 287).] =287.= The most recent form of catalogue sheaf is that illustrated in Figs. 107-8. It differs from the adjustable in having a rigid back, and but one screw. In other respects it is perhaps easier to manipulate than the binders just described. The holder consists of a strong wooden back to which two stout covers are attached by means of hinges, specially designed to guard against injury to the covers. Within the holder a special form of brass screw-fitting is mounted, upon which the slips are threaded, so that when the covers are closed the whole sheaf is firmly secured by means of a special screw. A few turns of the key suffices to lock or open the holder.