Use of the Ruling Pen
For straight lines the ruling pen should be employed. In this implement, the nibs, as in the pen compasses are provided with a screw, by means of which the pen can be adjusted to form thick or thin lines as required. Care should be taken in the adjustment; for the thinnest line the points should only be in contact. If screwed too tightly the nibs may be bent and would have to be re-set.
There is a limit to the thickness of line in individual ruling pens, which are made in varying sizes for fine or bold work. Bow and ruling pens should never be filled to the full capacity, as they are then liable to flood and blot the work. It is better also to charge the pen with the filler, which is usually provided with the ordinary liquid ink, or a brush; otherwise blotting may result. If the pen is filled by dipping, the nibs should be wiped dry on each occasion on the external faces.
In use the ruling pen should be held as vertical as possible, with the nibs perfectly parallel to the edge of T or set square, any divergence from the vertical might result in a curve instead of the straight line required. If the nibs are at an angle with the ruling edge, the ink will not flow freely, and there is also a tendency to cut the surface.