Brackets are used.
One bracket has a hole drilled for cables in the middle of tube (see pic.8).
All rotating can be locked for camera position by tightening screw (see pic. 9).
You can see approximate sizes of bracket on pic.10, 11.
Please , refer to pictures, I tried my best to show every side and all details, good and bad.
You will get what on pictures, take a good look and made your judgment.
NO RETURN.
If you have question, ask BEFORE, not after.