strongback

noun

1. The fore-and-aft spar extending from stem to stern on a lifeboat and serving as a raised spreader for a boat cover. (FM 55-501)
2. A strong bar placed across a hatch opening to hold hatch boards or hatch covers. (FM 55-501)
3. A load-bearing post with a T-shaped cross-section, where the short T-tail prevents bowing of the long post.
4. A backing pole used to reinforce and stabilize vertically-oriented sculptures.
5. A vertical structure used to support and stabilize a rocket, often hosting fuel and power umbilical connections. Usually retracted immediately before launch.