Just put the belt between the motor spindle and the roller. Make sure that the plunger of the select carpet and floor is in between so that when you select floor, the brushes do not spin.
Once the belt is installed it should be held between the spindle, and the brushes and the plunger held in between in an idling position.
This worked fine with my vacuum cleaner Kenmore Model#:116 39080000C. But I still don't know this is how it is meant to work in the first place because I could not find the manual on line.
Can someone give me a link to find it?
Priyantha, May 2008