Venetian Window with Stone Mullion and All Double Hung

When three pairs of sashes are used, the middle pair wider than the others it is called a Venetian Window The vertical divisions between the adjacent pairs of sashes are called mullions. If stone mullions are used in the window openings separate boxing may be made so that each pair of sashes is hung independently and the window becomes two or three separate window frames with the sill and head each in one length for the sake of strength.

If one sash only slides and the other is fixed in the frame the window is single hung sash and frame window. When both sashes slide and are balanced by weights, the window is known as a double hung sash and frame window.