Ken Siklflex is a good sealant if you never want to get the part back off again without damage. With windows you probably need to seal them annually or bi annually. For certain you will want to do it multiple times during ownership. Geoff has a multitude of sealers he uses depending on the materials needing sealing. He also primes the “glass” before applying the sealant. If you contact him at oceanswan@hotmail.com he'll tell you about his current favourites. Cheers Chrissie