Star LC-8521 User Manual page 20

12 Printer Setup
Unlock the tractor on the left (when viewing the printer from behind) by
pulling its blue lever up, and adjust the position of the left tractor.
Note that there is a guide inside the printer in front of the left tractor. The
mark of the guide indicates where the left margin of the printing will be.
Once the left tractor is aligned the way you want it, push the blue lever
back down to lock it in place.
Now move the tractor on the right to the approximate position of the right
side of the paper you are using. Pull its blue lever up to unlock it, and push
the lever back down to lock it into place. Also move the center paper
support so that it is approximately halfway between the two tractors.
Pin tractor Sheet guide Pin tractor
Open the covers of both tractors and align the paper so that the pins on the
tractors are inserted into the holes of the paper.
Close the tractor covers. At this point you can make final adjustments to the
paper position by releasing the blue levers and moving the tractors. The
paper should lie flat with no buckling or bulging (tractors too close) or no
stretching or elongation of the holes (tractors too far apart). After making
these adjustments, be sure that you re-lock the tractors by pushing the blue
levers back into their original positions.