Main lug only panels require a separate detach upstream; they're often used as subpanels when expansion space is

https://www.livebinders.com/b/3728064?tabid=7305b817-3c10-7a84-83eb-0576dd13c7e2

Main lug just panels require a separate detach upstream; they're typically used as subpanels when expansion space is needed in larger electrical systems.