Some people have been asking about the 'plastic thing' which you insert in the front of your hijab to make the peak stay up. It is basically just a strip of clear, very thin and flexible plastic, with rounded edges, and the one I have measures 12.5” x 2.5”. It reaches roughly from the top of one ear to the other. I wouldn’t suggest you try to make one out of plastic at home, because the edges will be jagged and so they’ll snag on your scarf. You could try it with thin cardboard though, but make sure that a single layer of your scarf isn’t too transparent, because it will look a bit odd!
To use it with a square scarf, fold the scarf into a triangle, then slip the plastic strip in between the two layers, to the very edge of the fold. Or you can wait until you've got the scarf on your head to slip it in. Then you just pin underneath your chin as usual. You will need to adjust it, and it takes some getting used to, but it means you'll never have to suffer the 'droopy peak effect' with your scarf ever again!
If you have any hijab shops/market stalls near you, have a look there as they usually have them. In the Middle East they usually give it to you free with a purchase.
This is what a hijab looks like with the plastic strip inside: