You're on the trail, it's a little too hot with that puffer or pullover and there is no room in your backpack. You need a solution. Have no fear, that bundle of paracord you've been saving in the garage has a manifest destiny and it's to be used as a loop on your backpack.
This simple but effective #Trailhack is useful and cheap. Function meets form meets additional space.
Macgyver Your Strap
Step#1: Measure a length of paracord that can attach to both sides of your backpack. Perhaps you have adjustment straps on each side, maybe you have to tie them to your straps at the top of your bag on each side.
Step#2: Loop around your bag straps on one side. In this case, it's 'mini-carabiner' clipped to each side.
Step#3: Loop around the other side and connect.
Depending on your comfort with securing, you can thread through the cord or tie it around. Regardless, you now have an affordable yet functional way to strap your jacket to your backpack.
Happy hiking and get out in the cold!