sidepost
nounUK /ˈsaɪd.pəʊst/
US /ˈsaɪd.poʊst/
A sidepost is a strong post on the side of something that helps hold it up.
The fence stayed standing because each sidepost was firmly in the ground.
OTHER MEANINGS
2. A secondary or less important post in a structure or organization.
He was given a sidepost in the company rather than the top job.
3. A post set at the side of a door, gate, or opening.
The gate swung smoothly on its sidepost.
4. A minor online post or message attached to the side of a main discussion.
Her comment appeared as a sidepost next to the main thread.