The first pic is a coupler lock made by Master lock. This is what I used on my Fleetwood. The shank is design to be broken in two differnt places for a custom fit to the size of the latch as showen in pic #2. You will notice that there is no excess of the shank behond the block which is the lock it self. Once there is a custom fit, it makes it much harder to bend the shank because leverage is reduced. Pic #3 is the coupler that is on my Rockwood as you have, this type of coupler lock will not work on our type of coupler because the rounded end of the shank opposit the lock will not clear the edge of the coupler to allow the shank to go thought the opening of the latch, but it will work on the older type of couplers that are raised up. This a fact, the more you spend on a lock the better the lock Is, Medeco and Schlage Primus locks are of very good locks for your house. Medeco has a left, right and straight cuts on the key and Schlage Primus locks have a security bar built into the bottom of the cylinder that has to be released before the lock can be open. Bump keys are used on cheap locks thay are very basic such as Kwikset and a standard Schlage locks with internal locking mechanisms( in side of a door) as far as exposed shanks like pad locks, everyone can get a master key, it's called bolt cutters.