Brother HL-4200CN - Manual (Page 60)

3 - 12 LOADING PAPER AND USABLE PAPER TYPES
8
Align the side guides with the edges of the paper.
Pushing the paper guides too hard against the
edges of the paper stack can cause a paper jam.
However, if the paper guides are too loose, the
paper may twist as it feeds through the printer.
9
Hold the paper tray with both hands as you align it
with the opening in the printer and gently place it in
the printer.
10
Push the paper tray completely back into the printer.
Do NOT use excessive force on the paper tray.
Doing so could damage the paper tray or the inside
of the printer.
An indicator next to the paper tray tells you how much
paper remains in the tray. Use this meter as a guide
for refilling the paper tray.