As the name suggests these rooflight have 2 panes , a vertical pane ( the up ) and a horizontal pane ( the over ) where the panes meet this is a glass to glass structural joint . Both panes finished internally and externally with a frameless detail , we supply and fit the powder coated aluminium cill the vertical pane sits on , and powder coated aluminium flashing to the top pane . This type of rooflight is particularly efficient at bring light deep into the room while offering a full view of the sky and garden .