How do additional curtain rail brackets work?

[Cinnamonandcoal]

I'm confused.
I have some heavy curtains to put up a across a wide window, so lots of weight.

Not sure if IKEA poles will be sufficient or if I need something more heavy duty.

Then I keep reading in online articles that for heavy curtains the pole may need additional brackets - not just one on each side and one in the centre. How does that work? Surely if there are extra brackets along the rail the curtains won't close because the rings won't be able to slide across?
I feel like I'm being stupid here but I don't understand!

They generally have one in the centre

You can get brackets that allow special rings pass over them.

Dunelm do them labelled as for bay windows.

Rings for that purpose are C-shaped.

Some corded poles have the runners inside with hooks hanging through a slot in the bottom.

We have long, heavy, wide curtains and use HD poles with a single central bracket (which of course the rings don't have to pass over).

Of course having decent poles is only part of the solution because if you don't have a good fixing it will all come crashing down anyway.