The image on a back patch is the same size as a T-Shirt image- usually around 10-12" long and about 10-11" wide. These are called back patches because most people put them on the back of jackets/vests, but they can also be sewn to the front of hoodies or shirts or whatever other piece of clothing you wanted to put it on. They can be safety pinned on, but sewing is definitely the better option. Don't worry, you don't have to be a seamstress! First, trim the edges to fit the area you are putting the patch on (there's usually about 1-3 inches of extra fabric around the design) To make sure it's straight, get a piece of cardboard the same size or bigger than the patch. Put Elmers Glue on the back of the patch and put it on the jacket- put cardboard on top and then something heavy on top of that. After about an hour the glue should be dry so you can sew the edges.