Used for clamping rulers and drawing lines, replacing right angle rulers. The A version needs to be polished and chamfered at the mating position. The B version has added chamfers at the mating parts to facilitate insertion. Scribers 1A and 2A: suitable for rulers with a width of 30≤width≤40. Scribers 1B and 2B: suitable for rulers with a width of 20≤width≤40.