Let's start out by creating a new file, I used a 500�400 pixels canvas with a white background set at 72dpi. Now choose your Rounded Rectangle Tool, above your screen under the options palette select 'Fill Pixels', 6 px radius and check anti-aliased. In a new layer draw a black rounded rectangle with 23 x 130 px dimensions, if you want a longer zipper add your own height settings. Then cut the top corners on the rounded rectangle.