Alpine routes are typically neither built nor maintained. They grew from being used traditionally over years or decades. Occasionally, dangerous and exposed sections may be equipped with protection such as wire cables, chains, abseiling points and bolts. This is kept to a minimum (die absolute Ausnahme, the absolute exception), for both the preservation of the environment and to prevent liability issues for those who install the devices. Climber Paul Preuss argued in 1911 about the use of aids such as pitons on alpine routes in his essay Artificial Aids on Alpine Routes.