I tried to shred a USPS priority mail envelope but the shreds merely wound around the shredder bar without dropping into the receptacle. When I tried to clean the shredder bar I could not because the material of the USPS envelope is much stronger than ordinary paper. I do not how to proceed without opening the housing. Thus my desire for an owner's manual. (See photo at : http://www.royalsupplies.com/Shredders/PX1201-Cross-Cut-Paper-Shredder-12-sheet.html)