This roof vent is very specific to a particular brand of greenhouse and is not suited for use as a retrofit in any other. When I read that it had a frame, I believed I could make it work but only the window is framed (as in, it is a single framed piece of greenhouse material) and not a moving window within an outer frame. That said, the vent mechanism is very nice and I'm going to make it work in my current greenhouse.

Not complete instructions (clear for beginner)