Very interesting image at first glance it makes you think what is it. The focus appear to be on the lock itself, the angle at which this was taken makes it interesting and not just a lock.
The spots on the wall in the right hand corner are distracting and pull you away from the main subject. The focus is a bit soft at the bottom and as I said appears to be on the lock but the lighting on the lock doesn't allow for any of the detail to be visable.
It does meet the challenge and has a lot of potential for making the viewer think what is it. =o)
5. Fits the theme well enough, and there are no blatant 'you suck!' flaws to it, but neither does it really grab me for any reason at all. For reasons of composition, cropping, or subject choice, it's just a photo, and doesn't do especially much for me, aesthetically.