Well, from my own hands on experience, ailerons on the Lockheed C-141. The seals are made from what appeared to be a heavy plastic coated canvas. They failed 80% of the time. Most of the planes flying would have torn seals, this was not a defect that would ground the aircraft. When the plane would come in for isochronal inspection you could count on changing them out. Lots of hard to reach screws and retaining plates.
More recently I've read that Boeing plans to seal some surfaces on a new model of the 737 designed for short take off and landing. I get to touch a lot of 737s, basically every new one, so when I see it happen, I'll let you know.