The main role: Before Chartwork for drawing lines bearing line or course, the degree or amount of bearing line degree course line.
Two hands each holding a ruler of David, alternately moved in parallel.
Usage: When the move operation, the appropriate force to suppress static hand -foot, one hand pushing moving feet, two feet alternately moved in parallel until the required position. Alternately moving, to prevent the static foot displacement.

colour:Transparent color
Material:plastic
size:450mm

Package Contents:
5*Chart parallel ruler