W20 Steel Windows – The traditional heavy-duty framing system, 32mm wide with 5mm thick flanges, originally developed for commercial and industrial applications. It accommodates single and insulating glass units up to 16mm thick in the same profiles simply with a change of bead. All glazing, whether in fixed lights or casements, is in the same plane.
It can be divided into small panes with tee glazing bars, having a table face width of no more than 29mm. Hinged casements, hung at top, bottom or side, and swing windows pivoted horizontally or vertically, can all be constructed from the same kit of profiles. Elemental coupling is achieved with simple slender transoms and mullions.