An astragal is a moulding profile composed of a half-round surface surrounded by two flat planes (fillets). An astragal is sometimes referred to as a miniature torus. It can be an architectural element used at the top or base of a column, but is also employed as a framing device on furniture and woodwork.
An astragal is commonly used to seal between a pair of doors. The astragal closes the clearance gap created by bevels on one or both mating doors, and helps deaden sound. The vertical member (molding) attaches to a stile on one of a pair of either sliding or swinging doors, against which the other door seals when closed. Exterior astragals are kerfed for weatherstripping.
An astragal may also be known as a “meeting stile seal”. It is sometimes confused with the wooden trim that divides the panes of a multi-light window or door, known as a muntin.