Features: 9-sided line: 9 horizontal lines of different heights can be drawn Anti-slip rubber ring: Used for line drawing pen non-slip Aluminum alloy material, laser lettering, durable Notes: Quickly distinguish between primary and secondary holes: six adjacent holes with scales and rubber rings in the holes are the main hole, and the other is the secondary hole Main hole scale: 10/12.5/15/20/22.5/25 Secondary hole scale: 17.5 (8.25 and 26.75 are not commonly used so they are not marked) Instructions 1. The vertical height measurement of the frame (or the interpupillary distance ruler) 2. Confirm the scale you want to use, find the corresponding hole position and insert the thin end of the pen from the side without the rubber ring Thick for head Thin for head 3. Turn the scale used upwards, and the corresponding number is the vertical height of the hole axis (pen core). Roll the scribe to switch the height of the scribe (if you need to use 17.5, pay attention to insert the line pen To the secondary hole) 4. Put the frame and the scribe on the horizontal table to make the scribe Package included: 1X Lining horizontal scribe