The AC units are held on with the bolts inside the RV, under the inside cover around the sides one bolt on each corner which should be snug not torqued tight. They are very durable if kept snug, and usually last as long as the AC units do, as that's when you replace gaskets and check roof. The Refrigerator vent cover should have enough room under the cap to see the blots that sometimes do need cleaning and caulking. The cap is usually held down from top by two blots that have sealant coving them. If you can't get at the area under cap you can take it off, clean and caulk, but it's usually sealed with heat proof caulk that last very long.