The best way to hold a fall is to get as low as you can and dig your feet in. You may need to use your ice axe as a brake. Ease of arrest will depend on: how hard the surface is, whether the edge of the crevasse is soft, the victim is hanging free or, the in is uphill or downhill from you. A downhill fall is always more difficult to hold.

Once you have held the fall you will need to create an anchor on the surface to attach the rope to. If you can dig down to the underlying ice you can put in a couple of ice screws and equalise them to create an anchor. If the surface is just snow you will need to build a buried ice axe belay, this is quite awkward to do while holding the weight of your partner. Make sure you dig the hole deep enough it will have to take a significant load, angle the slot slightly back and make the front wall as smooth as you can and at right angles to the direction of pull. Try to keep the front slot for the sling as narrow as possible and try not disturb the snow in front of the slot as this is what provides its strength. It is worth back filling the slot, it may be easier to do this once you have transferred the load to the axe.

Once you are happy with the anchor attach a French prusik to the rope leading to your partner clip a screwgate krab to this and loop the rope through the crab, then clip it into the sling coming from the buried axe. Push the prusik as far down the rope as you can, then very slowly shuffle down and across to transfer your weight from you to the anchor. As soon as the weight is on the anchor and the prusik is holding, tie the rope off in case it slips, a 'slippery hitch' followed by a half hitch works really well as it can be released under load.

You can then back up the anchor with anything else available - buried ski sticks or even a rucksack. Next attach your other prusik to the rope running into the crevasse and use this to protect yourself while you move to the edge to check your partner. If your partner is going to try and climb out you can help them by preparing the edge, kicking away the overhanging snow and preparing a bit of a ramp. If you are going to try and haul them out you will need to pad the edge to stop the rope cutting it.