Abstract: The buck frame is in a one-piece construction and is designed to be embedded in a poured concrete wall. The exterior of the buck frame is provided with reinforcing ribs, while its interior surfaces form a centrally-located boss, the side faces of which are provided with lips and grooves to releasably retain a window frame, made of four separate interfitting parts. A resilient polyurethane board is fitted between the lintel part of the window frame and the registering boss of the buck frame to provide for installation and removal of the horizontally-slidable window panes and also of the window frame parts.