Gaiters are primarily used to stop debris, water or snow entering footwear when walking year round or climbing in winter. In some circumstances they are worn with shorts to protect legs from thorny vegetation often found in Maquis and Garrigue biomes in Mediterranean countries. Although ankle gaiters do exist for use with approach shoes, most gaiters sit between the knee and the bulk of the calf, with a leash running under the arch of the boot and a lace hook to keep everything in place. In wet weather conditions gaiters are often worn underneath waterproof trousers, while they tend to be placed over waterproof shell pants for winter and Alpine climbing to protect the trousers from crampon tears. Certain types of gaiters are specifically made for use with crampons and feature reinforced crampon patches around the ankles, often with a compromise on weight. To allow for the overtrousers to work their magic, it is recommended to use membrane lined gaiters which will not impact on the trouser's breathability.