What are "rounders" and "blockers"?

I’ve run into a couple terms from the cowboy boot world that I don’t think I quite understand. Might others here correct or confirm my understandings? I’d like to get these on the wiki.

Rounder (Pattern)

I’ve seen this used sometimes for pattern pieces made from last taping, mean formes, or geometric methods, but covering just one side of the last—inside or outside—and not yet combined with the other side to make a complete vamp or counter cover pattern.

Blockers

I’m gathering this might mean a vamp cut out oversized for blocking/crimping, but not yet trimmed to the shape of the final pattern piece that will be sewn up to make a boot upper.

Some makers also speak of “blocker patterns”, which I take to mean patterns they keep for cutting out blockers. They may use a handful of blocker patterns, like small, medium, and large, and pick the closest one to work for a particular boot’s vamps.