Hi Martin & Ray, I cleaned my bathroom skylight by working off a set of stepladders & removing the 4 galvanized slot headed screws located on the outside of the skylight that secure the plastic skylight to its lifting frame, this allowed me to take the skylight off the van, The skylight outer skin is secured to the inner skin by the 4 screws you have already removed so both skins can now be cleaned seperatly & then refitted to the van.