HP Deskjet 6540 Color Inkjet Printer - Manual (Page 13)

To prevent paper from falling out of the Out tray, pull out the Out-tray extension, and
then unfold the Out-tray extension stop.
1. Out-tray extension
2. Out-tray extension stop
Do not unfold the Out-tray extension stop when printing on legal paper.
After the print job is complete, fold the Out-tray extension stop, and then push the
Out-tray extension into the Out tray.
3.6 Envelope slot (HP Deskjet 6540-50 series)
Use the envelope slot to print single envelopes.
HP Deskjet 6500 series printers
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