Ask Martin Chester: Why carry crampons in the backcountry?

Conventional mountaineering crampons for your boots are just that – for when the gradient, conditions or technicality make skinning impossible. On a bootpack up a steep tight couloir, traversing an icy col, or on a technical ridge line, sometimes you just have to get off your skis. If conditions are anything but deep and soft, you’ll need crampons for traction.
Think of ski crampons (also known as harscheisen, couteaux, knives) as an addition to your skins, to stop skis slipping sideways. Your skins take care of front/back slippage.
But skin across an icy slope and two things happen: the more you edge, the more you rely on just the ski edge (and less of the skin makes contact with the snow); while if you edge less to get more skin contact, you lose your downhill ski, ahem, downhill! Then you are like Bambi on ice – so get your harscheisen on and you can grip and traverse with relative ease.
In summary, if you are likely to traverse any icy, sun-baked or hard-packed/windswept slopes, take some harscheisen. If you are likely to encounter hard, icy, steep, technical or rocky sections that are beyond skinning, carry boot crampons.