When carrying a backpack, it is important to make sure that there is no gap between the back and backpack. Here are three tips to avoid this issue:   1. Make sure the straps of your backpack are tight enough. If they're too loose, the backpack will sag and create a gap.   2. Choose a backpack with a waist strap. This will help distribute the weight of the bag evenly and prevent it from sagging.   3. Adjust the straps regularly throughout the day. As you walk, the backpack will shift and the straps may loosen. By adjusting them frequently, you can keep the fit snug and avoid an awkward gap.