HP 1100A - Manual (Page 13)

EN Printer components 13
Printer paper input trays
Rear paper input tray
The paper input tray located closest to the back of the printer can hold
up to 125 sheets of 20 lb. paper or it can hold multiple envelopes.
Front (single-sheet) paper input tray
The single-sheet paper input tray should be used when feeding single
pages or media such as envelopes. You can print the first page on
different media than the rest using the single-sheet paper input tray.
Note The printer will automatically (priority feed) print from the single-sheet
paper input tray before printing from the paper input tray.
Printer paper guides
Both input trays have paper guides. Paper guides are used to ensure
the paper is correctly fed into the printer and that the print is not
skewed (crooked text on the page). When loading paper, adjust the
paper guides to match the width of the paper being printed.