Abstract: A window closure for sealing a viewing and access port in a glass forming chamber includes a handle pivotally mounted to a glass pane supporting frame, the frame being hinged to the wall of the forming chamber below the viewing port. The handle and hinging facilities are secured to the frame outside the perimeter of the port to provide an unobstructed view into the chamber when sealed, and to provide unobstructed access through the port when opened. The handle is provided with a pair of oppositely disposed hooks for engaging correspondingly located pins secured to the chamber wall. The closure is opened by pivoting the handle to disengage the hooks from the pins, and the handle is then used to rotate the entire closure about the hinge to come to rest below the port, parallel to the chamber wall. The closure further includes facilities for detachably securing the glass pane to the frame for easy replacement of the glass.