I called the supplier (C.R. Brophy) on the Brophy Non-Slip Adhesive Safety Strips, # NSAS, and they said they are designed for the steel and aluminum steps. They can be used indoors or outdoors.
As far as working on wood steps they did stay that the strips will adhere to the wooden steps they just do not know how long that the strips will last on wooden steps if used outdoors. They have only tested them for durability on the steel or aluminum steps. view full answer...