THE DETAIL OFFICE there is a different number for the material and for the classes of workman- ship, but this leads to an enormous notation, which would not seem to give commensurate results. To keep the cost number from being confused with dimensions or " numbers off " it is usually ringed thus: In the drawing proper, each part should have printed under it its dis- tinctive name and " number off ", also the scale to which it is drawn, if different scales are used in different parts of the same drawing. All spare parts required should be marked on the working drawings, so that they can be made at the same time as the working parts. Finally, at the foot of the drawing, its well-known title, such as " piston- rods " or " cylinders ", should be given, and the number of the job, draw- ing number, date of drawing, and scales. A characteristic title would be ENGINES No. 783 CYLINDERS SCALE: i J in. = i ft. 4 Sheets: Sheet No. i Drawing No. 783/1 The table of particulars set out at foot would be something like the following: Cost No. Particulars of Part. No. off. Material. Ordered. Order Sheet. H3 Junk ring studs 64 Steel 2I/II/2O P-63 114 Junk rings 8 Steel 23/11/20 Drg. 783/11 Colour Work.—In some offices a considerable amount of colour work is done, chiefly by juniors, generally to distinguish the classes of material used. Very faint washes only should be used for these, and these should be applied to black-and-white prints rather than to the tracing. There is a fairly well-known convention for materials, such as neutral tint for cast- iron, blue for steel, brown for copper, yellow for gunmetal, and light pink for lead. Sections are frequently hatched to show up more clearly and to indicate unmistakably that they are sections. Diiferent offices may have different conventions for colour schemes and for hatchings, but those shown in diagram are those in most general use.