ends must be reinforced so that the strength of the member shall not be reduced by the trimming.

In riveted tension members the net section through any pinhole shall have an area fifty (50) per cent in excess of the net sectional area of the body of the member. The net section outside of the pinhole along the centre line of stress shall be at least sixty-five (65) per cent of the net section through the pinhole.

Pins are to be proportioned to resist the greatest shearing and bending produced in them by the bars or struts which they connect. No pin is to have a diameter less than eight tenths (8/10) of the depth of the deepest eye-bar coupled thereon. No pin is to have a smaller diameter than two and a half (2 1/2) inches.

Lower chords are to be packed as closely as possible, and in such a manner as to produce the least bending moments on the pins; but adjacent eye-bars in the same panel must never have less than one-half (1/2) inch space between them, in order to facilitate painting. The various members attached to any pin must be packed as closely as practicable, and all interior vacant spaces must be filled with steel fillers, where their omission would permit of motion of any member on the pin. All bars are to lie in planes as nearly as possible parallel to the central truss plane.

In detailing I struts composed of four angles with a single line of lacing, the clear distance between backs of angles shall never be made less than three quarters (3/4) of an inch, in order to permit the insertion of a small paint-brush.

The greatest allowable pressure upon expansion-rollers of fixed spans, when impact is considered, shall be determined by the equation

p = 600d

where p is the permissible pressure in pounds per lineal inch of roller, and d is the diameter of the latter in inches. The least allowable diameter for expansion-rollers is two and a quarter (2 1/4) inches.

Rollers shall be enclosed in boxes made practically dust-