A (Mill Finish Aluminium) B (Mill Finish Extruded Bronze [Brass]) C (Clear Anodized) D (Dark Bronze Anodized) G (Gold Anodized) 

An Astragal seals the gap at the leading edge between a pair of door leaves. The pair can have 'plain' or 'rebated' meeting stiles—the design and suitability of the Astragal will vary accordingly between the two options. Astragals on external pairs of outward-opening doors commonly overlap Astragals, which protect against the weather and provide security as a lock guard. On internal doors, astragals protect against smoke ingress and provide additional security on locked doors.

Doors are typically the weakest link in any partition designed to have acoustic sealing properties. Astragals, perimeter gasketing, drop seals, and door sweeps can all prevent sound from leaking through cracks around the door perimeter.