Fourth. With the careful and thorough system of checking shop-drawings in vogue in the author's office, all the advantages to be gained by making complete working drawings are obtained by the much simpler method of making complete detail drawings.

Fifth. The manufacturer always appears to be better pleased and satisfied if the making of the shop drawings be left to him; and the work of manufacturing the metal proceeds more smoothly in consequence.

In starting a detail drawing, the first thing to be done is to lay out a sheet of standard size. If the subject be a framed structure, such as a bridge or roof truss, it will greatly economize space on the drawing if the skeleton frame be laid out on a small scale, say three-eighths or one-half inch to the foot, thus giving the proper inclinations of all members, and if the details at all the panel points and connections be made to a larger scale, say three quarters of an inch or an inch to the foot. The centre-of-gravity lines of all main members should coincide with the lines of the skeleton diagram. For the details of ordinary bridges the scales just mentioned will be found the most satisfactory.

It is a very common error among bridge-draftsmen, when two different scales are used, to make the principal lines of the main members continuous between panel points, thus exaggerating the apparent size of the said members. This is entirely wrong, and is often the source of serious errors in the shops. In such drawings, the main members should be broken off before their principal lines meet midway between the panel points; and it is often advisable to show a section of the member between the broken ends.

After deciding upon the scales, the next step is to determine what portions of the structure are to be shown on each sheet, if more than one is to be made, and what is the best possible arrangement for all details on each sheet so as to fill it uniformly and allow ample space for illustrating each detail in the requisite number of views. For short spans, up to say two hundred feet, by carefully arranging the details, everything can  be  shown  clearly  on  a  standard  sheet  of  twenty-nine  inches