>>19946326The "nipples" are always at the bottom of these structures.
Imagine how thick the wooden walls would have to be to hold back that much wet 'concrete'.
The water mooves downward causing the top to dry way before the bottom - especially if the water just pools and sits there.
The holes are cut in the bottom of the wood to allow the water to flow out causing some of the concrete to come out too and they were able to use the 'nipples' to determine when the mixture was dry enough to remove the panels.
