Usually skateboards, surfboards, etc. are not allowed in factories, due to injures.
The kids are allowed in the letter factory(to get in their clubhouse) while being rebuilt. Usually, no one, except the workers, are allowed in buildings being constructed.
When Quigley says "CT, burfder, some rousing music please," burfder spawns a trumpet. This is bad for 2 reasons, one is no 3 year old child can play the trumpet. 2 is that burfder turns into items. He doesn't spawn them.