A person who knows the history about the unloading and loading of a bin will have a better understanding as to what would be visible from the top surface.
Is the surface peaked, or is it an inverted cone?
In other words, have you cored the bin?
Are there conditions such as shiny metal or clean sidewalls that should be present when the grain has dropped from unloading?
If that grain hasn’t revealed a shiny or clean sidewall, that tells you that the top surface most likely has bridged, creating a potential for entrapment.
Reprinted from Grain Journal July/August 2020 Issue