Heavy, light-blocking (blackout) curtains are a necessity for my west-facing living room window. For a long time, I had black curtains because color choices were limited. Finally, I found purple blackout curtains at IKEA. :)
As with most things IKEA, the curtains are cleverly designed. They accommodate at least three different methods of hanging: rod pocket, back tabs, and loops for curtain hooks.
Alas, the pocket and tabs were too small for my large-diameter curtain rod. This left me with the loops. I would need curtain hooks to go through the loops, and curtain rings to hang the hooks on. This was not an ideal scenario for two reasons: large curtain rings are surprisingly expensive, and I didn't really want the look of visible rings.
It occurred to me that shower curtain rings would be large enough to fit on my rod... but how would I make them work with the curtain? Then came the "eureka" moment. I realized a particular type of shower curtain ring - thin metal, hinged so that it opens wide - would work perfectly. And they're inexpensive; just a few dollars got me two packages of 12.
Using them was simple. Open a ring and slide it through a loop on the curtain.
Close the ring. Repeat, spacing the rings appropriately.
Slide the rings onto the curtain rod. Done!