Cartography

7
Beam compass
Is an instrument used when it is required to draw a circle or arc whose radius exceeds that of 
the ordinary compass. It consists of three major parts, namely, points, an interchangeable pen 
pencil and one or more bars. The pen or pencil is attached by means of a sleeve which may be 
adjusted to the required length on the beam. Any further fine adjustment necessary is made
by means of the adjusting screw on the fixed head.
Parallel rulers
Consist of two straight edges fixed together in an adjustable form used as a straight edge 
when drawing a series of parallel lines. It is also, used to line up letterpress on fair drawings.
Generally flat on one edge and bevelled on the other. It is used as a guide when drawing 
straight lines or, cutting with a knife.
Care of drawing instruments, equipment and materials
1. Pencils:
Should be kept sharp, with those intended for ruling lines against a straight-edge to have a 
chisel point. Sharpened pencils should not be carried about in the breast pocket; this may be 
dangerous.