[Crowbob]

There are brackets with adjustable lengths on which are electrical boxes. These are mounted between the joists. Not meant to be exposed. Something like this:

https://i0.wp.com/litestoreusa.com/wp-content/uploads/2023/07/75806-Arlington-FBRS4200R-Steel-Fan-Fixture-Mounting-Box-with-Adjustable-Mounting-Bracket.jpg?fit=800%2C800&ssl=1