HP 2566C - Manual (Page 39)

Set the tractor control knob to the FORMS WIDTH ADJUST
POSITION (Figure 3-20, A). Only the right tractors should move; the
left tractors should remain stationary. Press the right tractor control
key to increase the forms width position (Figure 3-20, B). To decrease
the forms width position, press the left tractor control key until the
tractors are narrower than the form (Figure 3-20, B, HORIZONTAL
ADJ.).
2. Ai^ust the right tractor.
3-18 PREPARING THE PRINTER FOR OPERATION