The VELUX skylight was developed in 1942 by the Danish civil engineer Villum Kann Rasmussen (1909-1993). Made of wood, it was top-hung and had an external zinc cladding. It incorporated drainage channels for rainwater and had a tight seal, and it could be installed on a sloped roof. In 1945, Villum Kann Rasmussen developed a pivot hinge that made it possible to tilt the window sash back on its own axis without damaging with external cladding; this allowed both sides of the window to be cleaned from inside. VELUX skylights have undergone further developments, and today VELUX' various toplighting models are leading among international brands.