The chain on my bike keeps hitting this silver thing http://i223.photobucket.com/albums/dd239/MissMacle/DSC_1007.jpg(exactly where the rubber band is), but I have no idea how to move it and prevent it from doing that. I tried tightening and loosening some screws, but nothing seems to work. What should I do?
http://i223.photobucket.com/albums/dd239/MissMacle/DSC_1007.jpg

I don't think the other link was working.