ends of the block; these project from the bottom, and are buried in the bed material. The key is drawn to enlarged scale in Fig. 400; it is easily knocked out when a block has to be cut, and is re-inserted in a small mortise. A half dovetail groove is also worked on the side of each piece, which forms an additional key to the block. In Fawcett's system, shown in plan at B (Fig. 391, p. 94), and in isometric projection by Fig. 401, the ends of the blocks have a ⅛-in. groove cut across them at an angle of forty-five degrees, and these, when the blocks are laid in herringbone pattern, lie in a continuous straight line. Into these grooves a ¾-in. by 118-in. steel tongue is inserted as shown in Fig. 401, the succeeding row of blocks fitting over and completing the groove. This system is very effectual in preventing the rising of individual blocks, and is much used on fire-resisting concrete floors. The letter references in Figs. 391 to 399 not mentioned in the text are: C groove, D mastic, E cement, F concrete, G ground.
Fig. 400.—View of Metal Key.
Fig. 401.—Fawcett's Patent Block Floor.
Parquet Floors.
Parquetry is a method of covering a floor with hard and richly coloured woods, arranged in various fanciful and geometric patterns, the effect of the design being brought out by the various colours, and by the direction of the grain in the component pieces, which are selected chiefly for their differences in this respect. Usually, for the larger portions of the patterns, the natural colours of the wood afford sufficient contrast, but for bands in the borders, and for edgings for the geometric figures, more vivid colours are sometimes desirable, and these are obtained by dyeing some light-coloured wood, such as ash or sycamore, to the required tint. The three forms of parquetry in ordinary use are known respectively as thin, medium, and solid. The two former, which are respectively out of ¼-in. and ½-in. stuff, are glued to ½-in. or ¾-in. deal backings in squares or panels from 10 in. to 18 in. square, and these panels are grooved and tongued all round, or sometimes dowelled, and are attached to the counter-floor either with screws, which are afterwards pelleted, or by gluing down. The former method is employed when it is intended to remove the parquet at some future time; and the latter, when the parquet is to be permanent. The solid parquet is about 1 in. thick, and the various pieces are usually glued direct to the counter-floor and to each other in one operation, the design being formed as the work proceeds. In this method, all pieces more than 1½ in. wide are dowelled, or, in a cheaper class of work, are nailed to each other with wire nails. Borders are fixed first, and, as far as possible, these are made wide enough to bring all small recesses and projections into line, so as to cause no interruption in the pattern; but large openings must have the borders broken and returned around them.
