Lunch box handle

I'm confused about how to do what I thought should be simple, a lunch box handle. It's having the metal rings slide along the track in the handle in all the different positions. Any suggestions?

http://is.alicdn.com/img/pb/994/286/609/609286994_389.JPG http://www.lulusoso.com/upload/20120501/Tin_Lunch_Box_with_Handle.jpg