ones ; but when this is done it is often advisable to rivet a thick narrow plate to the under side of each channel, in order to facilitate the packing and detailing of web-members by keeping the centre line of stress coincident with the gravity axis of the piece.

Main vertical posts shall, generally, be composed of two laced channels, preferably rolled ones, although built ones can be used where large sections are required.

Secondary vertical posts may be built of two rolled channels laced, or of four angles in the form of an I with a single line of lacing. These secondary vertical posts should, preferably, be riveted to the top chord instead of being pin-connected like the main vertical posts.

The channels of vertical posts may have their flanges turned either inward or outward as desired, or so as to best suit the general detailing of the truss.

Stiff bottom chords and inclined web-struts may be made of either two channels with two lines of lacing or of four angles with one line of lacing.

Upper lateral struts, overhead transverse struts, and web-stiffening struts shall, preferably, be made of four angles with one line of lacing. In case, however, the said angles be spaced very far apart, as in lateral struts connecting deep top chords, they are to be placed on the corners of a rectangle, with their legs turned inward, and laced on all four faces of the box strut thus formed.

Eye-bars are to be used for all bottom chords and main diagonals that do not require to be stiffened.

Counters, when employed, can be of either rounds, squares, or flats. These and all other adjustable members are to have their ends enlarged for the screw-threads (unless soft-steel, cold-pressed threads be used) so that the diameter at the bottom of the thread shall be one eighth (1/8) of an inch greater than that of the body of a round rod of area equal to that of the adjustable piece.

In short spans, two angles riveted back to back, or even a single large angle, may be used for lower lateral diagonals; but for  long spans  the diagonals  are to be made of four angles