The ruler can be used as tools in the classroom to meet the measurement needs of teachers and students, it is also good tool for measurement in . The straight ruler is made of plastic, sturdy and durable, not easy to deform or damage, suitable to your repeated uses, you can to use without worrying about the quality. Can be used as an angle parallel ruler, straight line, horizontal parallel line, arc measurement, etc. Can be used as a protractor, 0-180 degree angle measurement or scribing (1 small grid 5 , a grid 15 degrees, the angle displayed by the dial, is the degree of opening of the ruler). The tip of the angled disc in the middle of the disc is the center point of the circular arc, which can draw a circle or arc of 4-30cm diameter. Put the ruler vertically, open the ruler 90 degrees, pull down the right scale in parallel, and draw a uniform parallel line. Open the ruler to a 30cm scale and draw a straight line. Type:Ruler Item:Drawing Compass Ruler Kit Item Type: Straight Ruler Size: .30cm/11.81inch color:White Material:plastic Package Contents: 1 x Straight Ruler Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.