daggerboard

1. (nautical) A retractable centreboard that slides out to act as a keel.Examples: "Route the bitter end of the cunningham through the hole in the daggerboard and secure it with a figure 8 knot. This keeps the daggerboard in the hull in case of a capsize."; "Push the boat the rest of the way into the water and insert the daggerboard."

2. (architecture) One of many decorative boards that form a valance for a canopy, particularly on older railway stations.Examples: "It will also have examples of its composite canopy daggerboards, which use CNC technology to produce replicas of historic designs - and which have been deployed as modern alternatives to traditional daggerboards in sensitive surroundings such as at Bath Spa."