Let me rephrase that, the cover slides forward to within a few inches of the neck of the hitch from the trailer. I can lock it in that position and I store a 9.9 Mercury 4 stroke under it against the rear wall of the pickup box forward of the hitch which puts it out of sight while on the road. When the trailer is not attached to the truck, the Retrax tonneau cover slides completely over the hitch in the box and again can be locked. This gives a smooth appearance to the truck and my hitch can't be removed (or stolen) from my truck while in a campground. I never remove my hitch from my truck so a hard lockable tonneau cover was the only way to go.
I also have 2 swing cases at the back of the box up against the sidewalls behind the wheelwells for storage, these are also lockable and can be removed.
The picture of my avatar shows my 12' aluminum boat on the front of my truck. It loads by a winch automatically. This is the web site for that company:
Load My Boat: Custom manufacture of recreational loading systems for vehicles
EIDE in the states also sells a similiar loader.
Hope this helps you.