They make a shelf attachment for the top of your ladder for the cube and it comes with an additional lock. I guess for the REAL serious crook who would climb up your ladder.:R
I have never seen them on the ground, every one I have seen over the past 2 years have been mounted on the top of the ladder with the optional ladder mount bracket. I personally would not leave home with my RV without a ladder mount for the Cube.
Here's the King Control Diagram of it. You can also buy them at Radio Shacks that are located in a touristy area where there are a lot of seasonal RV's.
http://kingcontrols.com/userfiles/file/20628,%20Rev%20B,%20MB400%20%20Bracket,%2011-10-08.pdf