The invention provides a structural assembly for use in a building comprising an elongate structural element for use in a frame (such as a window or door frame) in an opening in the wall of the building, said structural element providing an effective pocket open along one side thereof, and a sill which comprises an elongate plate-like element formed along its inner edge with an arcuate surface as seen in transverse section, whereby said sill is adapted for rocking motion about its inner edge, said inner edge of said sill being received within said pocket and said plate-like element extending laterally from said elongate structural element.The invention also provides a sill for use in the structural assembly, wherein the inner edge of the sill is formed into a part cylindrical scroll, and wherein the outer edge is formed with a drip bead which as seen in transverse section has an arcuate surface facing inwardly, for engagement with the outer face of a wall of the building adjacent to an opening in which the sill is used.