From the roof almost none…but these two types of skylights are designed to fill different needs. The deck-mounted skylight sits right down on the roof deck and the interior shaft extends into the skylight itself. This makes for a very finished look and is best for new installations on sloped roofs. The curb-mounted units are more like a skylight cap that sits over a 2 X 4 or 2 X 6 curb. They are used in retrofit situations where matching the exact size of an old unit is difficult or on flat roofs where the new skylight needs to be raised above the level of the roof deck. Both of these skylights can be flashed with either the VELUX EDL or ECL series flashing kits and both come in venting and non-venting models. VELUX also makes blinds and shades for almost all skylights, deck or curb-mounted.