I am sorry that I am not familiar with this term, but what does it mean to “close ratholes” when running a meeting?

At my old job a rathole was any kind of tangent that could drain resources, demanding lots of manpower with relatively small yield — something that caused us to lose focus from our primary projects.

Specifically in the context of a meeting, a rathole was any sort of go-nowhere thread that either had little value to the main topic of conversation or was better addressed by a small sub-set of the group offline.

A key feature of any rathole is that you have no idea how deep it goes; it may never end unless you simply stop digging. :)