YSK there are more than 3 US credit bureaus

Why YSK: Locking your credit with the main 3 places is not enough.

https://innovis.com/ have grown enough to require locking as providers are using them as a single check source.

There's also https://www.chexsystems.com/ which many banks use for opening checking accounts. They're unique because they handle accounts that don't show up in a credit report.