I moved into a house and found these handy widgets screwed into a bedroom wall. These widgets each consist of a hook-shaped piece of metal with a small clip that fastens a window curtain to the hook. These are very handy for keeping light from shining around the curtain while I'm napping.
This is completely separate from the rod that the curtain hangs from. They are at about breast height.
I wanted to buy some more of these, but I don't know what to ask for at the hardware store and it's tricky to describe it.