A movable window assembly includes a transparent sheet having a retention shield formed of a plastic material. An edge support is formed about at least a predetermined periphery of the transparent sheet and is adapted to cooperate with a channel formed in a vehicle window opening frame to retain the window assembly in the frame when pressure is applied to the window assembly tending to force it out of the frame. The edge support can have a reinforcing core and can be molded in situ on the transparent sheet. In an alternate embodiment, the edge support and the retention shield can be molded on a transparent glass sheet at the same time.