The Sewn On base does what the name says, it is designed to be sewn on directly to a heavy top, preferably a leather jacket/motorcycle jacket or a heavy combat shirt. Once attached it will be able to accep the 3rd Person Mount (Polly) sold separately on my store.
The mount is designed to contour the shape of a shoulder and has a lot of openings to run a needle and thread through. Check out the video below to better undestand how the system works.