4x15 transparent plastic protector plotter is designed to measure courses and bearings on charts and plotting sheets. Use for drawing a course and bearing from a given point, moving a line parallel to itself or plotting celestial lines in position. Printed in two colors for quick accurate selection of needed points and scales. Calibrated in degrees, nautical miles 1/40,000 and 1/80,000 and also in statute miles 1/40,000 and 1/80,000.