Jim, I have the same metal pinch system as Peters, took pictures, they are not as clear as Peters, do not know how to post pics in this message. The only reason column my not be locking is that the plastic handle has broken away from threaded stud and you may be able to put a locking nut or two nuts locked together, where plastic has broken, to the left side of the washer, then tighten them to hold column!
Don
Don