Prior arrangements for positioning line guides on copy holders have included magnetic devices magnetically attracted to the copy holder (See U.S. Pat. No. 4,267,656). Other techniques have included guide rollers on a T-square associated with a grooved element attached to a drafting board (U.S. Pat. No. 694,389). Flanges attached to drawing boards have also been disclosed for guiding T-square movement (U.S. Pat. No. 2,451,289).
None of the prior devices provides a satisfactory arrangement without the disadvantage of magnetic elements which can interfere with the operation of nearby equipment.