Perfect diagram, thanks! I made a little LEGO linkage to help me understand the over-center locking part. If I interpret this statement correctly,
the linkage would look something like this?
I just realized the red could be flipped upside down and still work. So if I were to put my understanding into words, gravity acting downwards wants to force the linkage outwards (left and right in the diagram) but the ‘grabbing’ force represented by the pink arrows opposes this. If you had to actually design this, what would you use to hold it tightly?