This is a great technique that I love to do. It is so easy but makes a card look so awesome! All you need is a window sheet (like an overhead transparency). Stamp your image on your cardstock in a dark color . Then stamp the image again on the window sheet , flip it over and line it up with the original image on your cardstock and then gently rub the back of the window sheet so it transfers to your cardstock. Sponge over the center of the images where they overlap and voila, you are all set.