A ski patrol is an organization that provies first aid and rescue services to skiers and participants of other snow sports, either at a ski area or in a back country setting. Patrollers are trained with the first aid necessary to stabilize and transport casualties to advanced care, often as EMT-Bs or the National Ski Patrol's equivalent Outdoor Emergency Care (OEC) technicians. Patrollers can also be EMT-Is or paramedics. Due to the remote location and terrain, transportation is often limited to toboggan, snowmobile, snowcat, and helicopter. Patrollers are often well versed in avalanche search and rescue and other specialized techniques (e.g., chairlift evacuation, helicopter rappelling). Patrols work to promote ski safety, enforce area policies (where applicable), and help injured skiers when necessary. Ski patrollers also work to set up the mountain before it opens by conducting trail checks, providing avalanche control work, and setting up necessary equipment in preparation for the day. At the end of the day they also conduct a sweep clearing the mountain for off-hours.