This is a simple trick I learned while in the military. It makes your jacket more portable by freeing up your hands. This is done by turning almost any jacket into a satchel. Some great things about it are that you can also put other things inside of it, using it as a satchel, or use it as a pillow for long hikes or camping excursions.
Step 1: Stuff Your Sleeve
Place one of your sleeves out flat and start shoving the rest of your jacket into it. If it starts getting to bunched up in the end your stuffing reach into the opposite end of the sleeve and pull some of the bulk down towards the wrist of the sleeve your stuffing.
You should end up with a sleeve that looks like there's another sleeve coming out of it, as seen in the second last photo above.
Step 2: Make a Satchel
If your jacket has no buttons you just shove the end of the sleeve into the wrist end of the sleeve you stuffed.
Step 3: How to Properly Wear and Adjust
When you wear the "jacket satchel" the wrist end of the sleeve that is stuffed should be at the bottom side below your armpit. If you put it up top on your shoulder it will keep separating.
To adjust it simply pull a bit of jacket that is stuffed into the sleeve out so your satchel strap is longer.