HP Deskjet 6122 Color Inkjet Printer - Manual (Page 19)

set the paper size
The 250-Sheet Plain Paper Tray can hold Letter, A4, Legal, Executive, and B5 sized
paper.
To set the paper size, you must set all three size adjustments located on the lower
tray.
Follow these steps to set the paper size in the 250-Sheet Plain Paper Tray:
1. Remove the lower tray from the base.
2. Slide the paper width guide until the arrow is even with the correct setting.
1. align the arrows
Set the width to LTR to use legal-sized paper.