I purchased the following blackout curtains and curtain rods;

https://www.amazon.com/gp/product/B00PF72QZK

https://www.amazon.com/gp/product/B00KCMJ2DW

I have an office that faces the rising sun and while I do not feel they help with thermals, holy fuck do they make this room a dungeon. It's dark in here. Like if you are not running a screen or a light, you don't see what you're doing.

I hung mine pretty poorly too, when I should have purchased curtains about 2 foot longer and put the curtain rod as far up as possible I only put the curtain rod about 1" above the existing mini-blinds. If I had put it about 8 inches above that, it would basically be impossible to see light leaking through. Right now, some light leaks through but only enough for you to tell where the top of the window is.

Another thing that I did was over-lap the panels in the center, because I have no intention of opening them. On one side I overlapped the end on itself also, this made it so the fold would naturally press itself against the wall forming a light seal on that side. I only did this math on one side though, so there is a 2" corner on the other side without that same seal but again- if I had simply bought longer panels and put the curtain rod further up... with the lights off you would think you were in a windowless room.