On 01/04/10 10:38 AM, Tom Crispin wrote:

Waterproof trousers over gaiters is probably the best option in heavy
rain, but in snow the gaiters should be worn over the waterproof
trousers where there is a risk of a self-stabbing by crampon;
hopefully the tough fabric of the gaiter will prevent damage to
expensive waterproof trousers.

For ice climbing this is the case, but for XC skiing the trousers won't
be damaged by anything. the classic knickers, with the gaiters over
them, is what used to be common for XC skiing before knickers went out
of fashion. Now with the plastic boots for back-country skiing there is
no need for waterproofing, but you still need gaiters. Some of the
higher end winter pants have integrated gaiters (along with a GoreTex
membrane of course).