Abstract: A light-blocking head-rail, and architectural coverings incorporating the headrail, include a light-blocking strip adapted to block out light. Embodiments of the light-blocking strip include bristles which tend to block substantially all of the light that might otherwise pass between a top surface of the headrail and a top beam of an architectural opening. The bristles can conform and fill in gaps between the top surface of the headrail and the top beam, and can further be compressed by a bracket connecting the headrail to the top beam of the architectural opening. Additional embodiments of the light-blocking strip are made from a flexible material that can be easily deflected and compressed when installed within an architectural opening.