The main function: Used for chartwork to draw bearing lines or course lines, indicating the degree or direction of the bearing or course. Two hands each hold one end of the parallel ruler, alternately moving it in parallel across the chart. Usage: During operation, apply slight pressure to keep one end steady while moving the other end. Move both ends alternately in parallel motion until the desired position is reached. This prevents displacement of the stationary end. Size: 450mm Material: Plastic Color: White Package Contents: 1 x Chart Parallel Ruler Note: The package includes only the items listed above. Other products are not included. Lighting and display differences may cause slight variations in color between the image and the actual item. Measurement may vary by +/- 1-3cm.