The skivvy roll was perfected by the United States Marines. Sometimes it is referred to as the grunt rolls. The skivvy roll is a method for packing a shirt, underwear, and a pair of socks into a compact, pill-shaped bundle that creates additional space. This is one of the most efficient packing techniques and allows you to get more light weight gear inside your ruck or EDC bag.
In the military it is very important to keep all your gear inside your pack. Everyone hates a gypsy camp of a pack (See picture for reference). Don't walk around looking like a crazy prospector with pots, pans and a pick axe hanging off your pack. Chances are very high that you will loose something and get hung up in underbrush while moving.
Here is the step-by-step guide to creating your own skivvy roll.