these louvers have brackets that sorta hang on the trim and are affixed to the window with double sidded sticky tape. I have some thick cusiony tape I was going to use. I'll get some pictures. It has holes for 4 brackets, I only have 3 of them. it should be easy enough to find something to use for a 4th. basically its just something that's screwed to the louvers and then taped to the window and is hidden by the edge of the louvers.