Catalina Direct has kits for those type windows. The two screws on each end hold the two halfs of the frame together. A good tool for acess to them in a Chapman Mfg. screwdriver set I have used one or the past 40 plus years. email@example.com . The Catalina kits include PVC gasket for the glass, Dow Corning 795 Silicone sealant,for the glass to PVC and 2M 4000 UV fast cure for the frame to gel coat seal.