As a 1P and now 1K, I always book myself into the exit row window when I am not at the front of the bus.

I have read threads that UA will 'block' a middle for a 1K or GS but this is not mentioned in a UA policy anywhere as it is probably not a 100% of the time rule. I did search on FT for this topic but the search function is down at the moment. 2 questions:

1. How do you know if a middle seat has been blocked for you?

2. Am I better off booking into a regular E+ seat and hoping for the 'blocked middle' or taking the safe bet w/ exit row? Does it depend strictly on load?

I realize that the easy answer is to upgrade to to C/F but that's not the point of the thread !