Timbers placed as A in [fig. 7] give rigidity to the standards by preventing flexure, and are necessary when the lengths of the uprights exceed 30 times their least diameter.
The deals used for braces are bolted to the standards; for poles, tying is resorted to.
Working Platforms.—The working platforms used in conjunction with overhead or overhand work depend upon the requirements of the building.
By over head or hand work is meant that the material upon which the mechanic is to be employed reaches him from over head or hand.
When no outside scaffolding is needed, the platforms are laid upon the floor joints in the interior of the building, being raised upon trestles as the work proceeds, and until the next floor is reached.
Light forms of scaffolds, as the ordinary masons’ and bricklayers’ pole scaffolds, are now frequently used as working platforms in connection with the Scotch system.
The South Country System.—This system is divided into two classes according to the strength required. For the first, square timbers are used; for the second, poles are employed. The scaffolds built of square timbers are known as gantries and stagings, and the pole erections are termed bricklayers’, and masons’ or independent scaffolds.
Gantries.—The term gantry was originally given to erections constructed with a view to the easy carriage of heavy material, but of late it has also come to mean a structure arranged to support lighter forms of scaffolding over footpaths which have to be kept open for public use.
Fig. 8.—Elevation of Gantry for Traveller