There is a Ryanair 73-200 sitting in an FLS Dublin hangar for 1 1/2 years due to this problem. It was in for a heavy C check which included a Lap joint inspection. The procedure fir this lap joint inspection was to cut out the lap joint,s and put in a very big repair. this was easier and more cost effective than lots of medium to small repairs. This did not include the lap joints over the wings. When the lap joints over the wings were inspected they discovered damage to the skin due to knives being used to remove sealant. They then decided to inspect the butt joins for simular damage and found the same. At this stage it was decided that the A/C was not worth repairing. I looked at these knife marks on the skin myself and they were deep. This was the first Ryan Air A/C found with this damage and opened this particular can of worms. Some of the other Ryanair 73-200's were inspected in the same facility and were found to be ok, some knife marks but repairable. You can see on the Ryanair 200's which A/C have had this lap joint Inspection/repair done to them, by looking at the lap joints over and below the window belts forward and aft of the wings there is a huge repair running the legnth of where the lap joint was.