Abstract: A frame and muntin assembly for use in a window or with another thin panel for a building structure. In a window the frame has interconnected frame members extending along the periphery of the window pane and each having an elongated outwardly protruding segment located outside the periphery of the window pane and offset in front of it, an elongated blind groove between the outwardly protruding segment and the periphery of the window pane, and an elongated inwardly protruding segment offset behind the outwardly protruding segment and engaging the front of the window pane. Muntins extend across the front between different locations along the grooves and are attached to the frame members by fastener elements received in the grooves. The muntins are flush with the outwardly protruding segments of the frame members.