I have a 1951 vintage Uggie and it threw me a bit the first time I had the locks off because the cocking rods have a spring which lifts them up (or pushes them down, I can't remember) into the way when replacing the sideplates. You need to press on the cocking levers at the front of the frame to get them into position for the locks to go back on. I don't know if any other sidelocks are similar?
CHAZ