When I have trouble remembering how to thread my model 15 clones I like to watch this video showing how to do it. This video was made by one of QB members, Muv:
http://www.youtube.com/watch?v=H2tii...eature=channel
If you don't want to watch how to fill a bobbin then just skip ahead, in the video, to 2:42 minutes--that is where the threading of the machine starts. All of her videos are wonderful!!