Also called trusses, these are U
-shaped metal reinforcement members, attached to the inside of the door to add strength and rigidity. Struts are necessary on wide, heavy doors to help prevent sagging and bowing in the horizontal position, and to provide additional reinforcement to comply with the required wind loading.
![Struts](https://www.garaga.com/sites/default/files/00_Garaga/KnowledgeCenter/Lexique/PontBridge_strut.jpg)