Windows and some doors in Spain have these wonderful metal shutters that slide down over the window from the top, both securing the window and providing darkness for sleeping.
They can be adjusted to let in just a tiny bit of light or dropped completely for total darkness
I have watched many people give up in confusion - so here is a quick lesson
The shades are operated by a sturdy strap usually mounted on the wall to the right of the window.
To CLOSE the shade, grab the strap at the very bottom and pull straight out away from the wall. Then gently let the shade drop, controlling the speed with the strap. You may have to do this two or three times to drop the shade completely.
If you want, you can leave the shade open just enough for light to come through the slits.
To OPEN the shade, simply pull straight down on the strap.
That's it! Easy as pie!