Not having much to do this popped into my head. I’ve searched the Softball Forum but didn’t see where this may have already been discussed.

Outfield wall with flat top. Fly ball is hit to outfield and hits front top corner (edge) of the wall.

1) Ball goes out of play. Home run? Ground Rule Double?

2) Ball comes back onto playing field. Home run? Ground Rule Double? Playable?

3) Ball bounces up, hits flat top of wall, goes out of play. Home run? Ground Rule Double?

4) Ball bounces up, hits flat top of wall, comes back onto playing field. Home run? Ground Rule Double? Playable?