Oce OP33 Reference Manual page 272

8
9
7
10
11
7-26 Envelope Feeder Attachment-B1
Fix the front width guide of the cassette in place, using the screws.
Adjust the back width guide of the cassette, as in steps 7 and 8.
Load the envelopes.
After checking the size switch, store the envelope type on the
Additional Functions screen.