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Using your forefinger and thumb, pinch your upper eyelid. Be sure to grab the outer ridge of skin on your eyelid, not just your eyelash, as this may lead to you pulling out some eyelashes. Once you've got a good grip on your eyelid, pull it up above your eye, around where your eyebrow is. This will probably feel strange, so don't freak yourself out! In one smooth motion, use your thumb to press your eyelid against the bone under your eyebrow (the supraorbital arch) and withdraw your forefinger. Your thumb will then be holding your eyelid up against your face without your forefinger. Now, with your thumb, gently push your eyelid down so that it folds over itself and flips inside-out. The push-force should be more against your face as you lower your eyelid with your thumb. This is so your eyelid doesn't slip from under your thumb. Follow the same steps you used for your other eyelid. If you're not ambidextrous, this may feel very awkward, but after a few tries you should begin to get the hang of it. After you are satisfied with your friends' freaked-out reactions, you'll probably want your eyelids back in normal, functioning order. Simply look up really hard with your eyes or blink really hard with your eyelids to return your eyelids to normal.

Summary:
Pinch your eyelid. Pull your eyelid up. Press your eyelid. Push your eyelid down. Repeat this process with your other eyelid. Return your eyelids to normal.