If you downhill ski or snowboard when it's very cold, you need a face mask. This is particularly important on the ski lift, when you are not exercising and can easily get chilled. It's also important at the summit, where the air is much colder. Once you are moving down the mountain, you may find that you are warming up and no longer need to cover your face. In that case, you can just roll the ski mask back up into a hat.
Take your beanie ski hat and turn it inside out.
Put the ski hat on over your face.
Use the measuring chalk to draw an outline of your eyes, mouth and nostrils.
Take the hat off.
Cut out the eye, mouth and nostril holes.
Thread the needle and then sew the edges to make finished holes.
Turn the hat right-side out and you have a ski mask,