Also known as parting bead. Usually a 3/8” by 3/4” or 1/2” by 3/4” wood piece. Designed to fit in a dado into the pulley stile. Usually held in by a compression fit. Designed to separate the upper from lower sash. Removable. Usually replaced with new.
In a double-hung window, a strip of wood applied to the jamb to separate the sash.
Weather stripping that prevents air and water infiltration. This is commonly found at the head and side jamb of a double-hung unit.