What it is is a cover for my Iriver Story, my e-book reader. You can buy them, but they are expensive and the ones I´ve seen are made of leather, which I try to avoid in things that I touch a lot (because of my colofonium-allergy).
What I did was, I took an old plastic folder from my schooldays, cut it to the right size using regular scissors, then I punched holes along the edge of one side, using punch pliers.
After that, I crocheted a square the same size as the reader (crocheted squares are less elastic than knitted ones, usually), and crocheted it, using a very small hook, to the plastic folder, with dental floss. I could have sewed it on as well, but I prefer crochet if it´s at all feasible, since I don´t need to cut the thread until I´ve used exactly as much as I need. Floss is superstrong and excellent to use for repairs to backpacks, trainers and such.
Finally I punched one more hole to the edge of the other side of the folder, where I tied a covered rubber band, to thread over the whole thing and hold the cover together.
I´m darned pleased with it, didn´t have to buy a single thing for it, and it took me less than three hours to make. The only thing that was a little hard was punching all those holes, my hand still hurts a bit...