Go to any rv parts store and ask them for a roll of putty tape. It is cheap and common. When you take the window out and have cleaned all the surfaces, you unrill and apply a bead of the putty tape where the window seals against the side of the trailer. Push the window back into place, and while someone is holding it from themoutside, go inside and reattach the cinch ring. Carefully toghtening the screws a little at a time until things are tight. I follow this with some Dicor. They make two versions, lap sealmfor horizontal surfaces, and one for verticle surfaces. Be sure to get the right one. If you have one window leaking, guaranteed the others are not far behind. Do them all and youll be good for years to come.