Let me try and be specific for this problem. The 2x3 Pacemaker Crown and Speed Graphics have a seam on the bottom of the bellows and the seams have a tendency to separate. Take the front standard off of the rails to get a better working access to the lower side of the bellows. Coat both sides of the separation with contact cement and let the contact cement get tacky (10-20 minutes). Press the separation back together with the folds aligned and then let everything cure overnight.