=147. Adjustable Shelf Fittings.=--The old-fashioned varieties of shelf adjustments for wooden bookcases, such as pegs fitting into holes drilled in the uprights, one and a half or two inches apart, wooden or metal ratchets for carrying bars or rods for supporting the shelves, and similar devices, may be dismissed as unsuitable for modern library purposes. The best-known adjustment is that known as Tonks’, from the name of its patentee. It consists of metal strips, with perforations at inch intervals, let into grooves in the uprights, and designed to carry the shelves on four metal studs or catches, which engage in the slots or perforations. This method requires very careful fitting, as the grooves in the woodwork must be deep and smooth enough to admit the catches, and each metal strip must be accurately inserted so that the slots will come level not only with those adjoining, but with those on the opposite upright. The least carelessness in fitting will cause shelves to rock and buckle, because not supported by catches all at one level. The illustration on page 145 (Fig. 33) will show exactly the form of this fitting. It consists of: shelf supported on standard; perforated metal slip and stud; and groove in wooden standard. [Illustration: FIG. 32.--Wooden Wall Case with Lodged Base (Section 146).] It should be noted that this variety of shelf fitting does not give absolute adjustability, but only a movement of about an inch up or down, as may be required. Smaller adjustments are impossible by this or any other similar system. =148.= There are various other methods of fixed shelf adjustments for wooden bookcases, English, American and German, but none of them possess any particular advantage over Tonks’ variety. Absolute adjustability in shelf fittings, as applied to wooden cases, has been obtained in the English method, to be seen at various libraries in England. There are also various American systems. Both of these forms are similar in principle to the absolute adjustments described under Section 149, but the English system was the first to be patented, and therefore ranks as the pioneer of this type of shelf fitting. [Illustration: FIG. 33.--Wooden Shelf Adjustment (Section 147).]