I think it's this: https://app.leg.wa.gov/wac/default.aspx?cite=110-300&full=true#110-300-0145 https://app.leg.wa.gov/wac/default.aspx?cite=110-300&full=tr...

I think it's this: https://app.leg.wa.gov/wac/default.aspx?cite=110-300&full=true#110-300-0145 https://app.leg.wa.gov/wac/default.aspx?cite=110-300&full=tr... >(6) Licensed outdoor play areas must be enclosed with a fence or barrier that is intended to prevent children from exiting and discourages climbing. If the outdoor play area is enclosed by a barrier that is not a fence, the barrier may be a wall constructed with brick, stone, or a similar material. For some background a co-worker's wife works at one of the outdoor preschools and said that in order to be full time you have to have a fence in play space next to the indoor school.