[header] How to shorten backpack straps [title] Put the backpack on and adjust the straps. [step] The cushion on the top of the strap should rest evenly and comfortably on top of your shoulders. The backpack should not sag below your behind. 
Instead, it should run parallel to your back when you are walking. [substeps] If you notice the backpack sagging below your behind, there may be too much weight in the backpack or you may need to get a backpack that has a reinforced bottom so it does not sag.