Abstract: A device and method for folding the main and secondary flaps of self-sealing envelopes into the inoperative condition. The envelopes (11) are fed, bottom edge leading, into a roller (20), the front panel of the envelope being in contact with the roller. The bottom edge lifts off the roller and the envelope is arrested and temporarily supported by abutment means (38,40,44) while the main flap (16) of the envelope is held to the roller by suction (22,24) and carried around the roller and thereby folded relative to the front panel of the envelope. In this position of the envelope, the secondary flap (18) slidably engages the surface of the roller and is then arrested by stop means (28) which carry the secondary flap (18) around and fold it relative to the back panel of the envelope.