In the traditional silk-screening approach, you start with a square wooden frame about the size of a T-shirt. Over this frame you tightly stretch a piece of sheer fabric (originally silk, now polyester). This is the screen. Over this sheer fabric you put a thin sheet of plastic into which you have cut holes where you want ink to appear on the T-shirt. You can either cut the holes with a scalpel (an arduous task), or you can use a liquid plastic coating that's sensitive to ultraviolet light and "cut" the holes with light.

Next, you place your T-shirt on a flat board and press the screen onto the fabric. By coating the screen with thick ink using a sponge, you cause the ink to flow through the screen onto the T-shirt. For multi-color designs, you do this multiple times, starting with the lightest color and moving up to the darkest.