There are two likely explanations for skis that slip, skid or chatter down a fall line. One is poorly tuned edges. The other is inaccurate body movements, especially in your ankles. To make the most of your skis’ shape, keep their edges engaged with the snow throughout the turn by rolling your ankles over your active edges. “The key is pressuring the inside edge of the outside ski,” says instructor Andy Docken. “When your anklebone is aligned over that edge, the ski will grip and cut a clean path through the snow.” On a moderately steep slope, carve different-sized turns while paying attention to the action of your ankles, pressuring the inside edge of your outside ski. You’ll feel an immediate difference. Andy Docken is the director of the Aspen Highlands Ski & Snowboard School in Colo.