Support

From DwarfFortressWiki

Supports are pillars built to prevent cave-ins. They can be linked to levers, and they will blow when it is pulled, causing a cave-in if the support was the only thing holding the roof up.

Supports are built through the build menu and require one piece of wood or stone to build. Unlike built walls they require an architect to be constructed. Dwarves can go through tiles with supports. Fluids can flow through them.