My Ortleibs have hooks that are opened with the carrying strap and sometimes need to be closed with it. A straight up pull opens. Pulling out and down closes. I usually don't have to close the hooks when I drop a loaded pannier onto the rack but usually do when the panniers are empty. I think you have the same hooks.

My panniers are the smaller front ones from 1999 and 2009. I have replaced hardware a couple of time. Love that I can just walk into a shop, have them order it and a week later, the bags are mounting like brand new. (And thank you, Ortleib for not obsoleting them.)