Abstract: In a dual sash window assembly having a pair of overlapping sashes mounted within an outer frame for relative horizontal movement, the outer frame has a stepped sill, with a pair of parallel spaced rails formed thereon as upward extensions from the risers of two of the steps. Mounted on the respective rails for rolling movement therealong, the sashes have bottom horizontal frame members carrying weathertight sealing strips arranged to make sliding engagement with the exterior surfaces of the respective risers of the sill. The sealing strips serve to make the window perfectly weathertight in spite of the presence of dust outlets formed by cutting away parts of the rails.

Abstract: A form into which concrete is to be poured has several abutments formed in prescribed positions on its bottom. The outer frame of a sash window or the like, which is to be built into a concrete panel to be cast in the form, is placed in the form so as to closely surround the abutments. The outer frame is further removably secured to each abutment by a horizontal bracing rod. A holder frame is placed over the outer frame to urge the latter into tight contact with the bottom of the form.