RE: Lock
I struggled with the same problems after I purchased my 6x10......only I need to store my trailer behind my garage which means pushing/pullling it through about 40ft of grass.
I bought one of those dollys in the post above and it worked great in the driveway.....I could manuver the trailer anywhere I wanted almost effortlessly.....but pulling it through the grass was another problem all together.
My solution was to find a used 1/2hp electric motor with a 60:1 gearbox. I then had a chain sprocket welded to the hub of one wheel. The 2nd wheel is on an axle that is attached to the wheel/sprocket so both wheels are driven.
A little bit of wiring on the motor gave me forward/reverse and an on/off push-button so I can precisely park the trailer when I done with it.
I found the dolly at a local Menards for $29.....the motor/gearbox I purchased used for $100.....some misc parts/chain/sprockets.....another $50. This is much much cheaper than purchasing one of the ready-made electric dollys meant for much bigger trailers (they retail for $1000 +).