Remove the shoulder strap from one side of your notebook
carrying bag. String it through the handles for your hand and
reattach the shoulder stap again on the side.
Now it should look like this if you hold your carrying bag
by the shoulder strap.
To mount this masterpiece, it is best to stretch both arms
up and to lift the bag at the same time. Then insert one arm
through one side of the shoulder strap.
Then insert the other arm through the other side and let
the whole thing slide down on your shoulders.
Voila! Now your notebook or laptop computer is riding
comfortably on your back. You have both hands free for
biking, carrying stuff or whatever!
To unmount this contraption, pull the shoulderstraps away
to the sides and the bag will start to slide down on your
shoulders and arms.
Be prepared to catch the bag when it reaches the end of
your arms. There you go!