I have an AEG Competence which looks like the illustration for D4100-1. There is 'Black Line' written on the door of the bottom oven. I want to clean betwwn the glass plates in the doors. I don't have the instructions which came with the cokker that is >10 years old. I checked the instructions in the user manual but the inner glass on my oven is inserted within a metal surround and does not appear to be removable in the way described in the manual. Can you help?