I used 3M double-sided Super Strong Automotive Attachment Tape, 1/2" wide x 5 ft., available at an automotive supply store for $8-9, 3 years ago for this. It's easy to do, has held very well, and shows no signs of separating. I do prints from 35mm and 645 negatives so I move the upper bellows up and down regularly and there has been no problem. This roll of tape is twice as much as you need. I looked for the black version but they only had the brown/beige and it was fine because when you join the bellows to the metal plate there is really no thickness to the tape.