The blister

The given template. Use a electric sander to ensure the edge of the hole of the template smooth. Place the aluminum sheet between two parts of the template and tightly fix them with the screws. Smash the aluminum with the nylon hammer to make the bottom part of the blister deepest. I rubbed a timber with the sander to make it into a sharp shape. It helps to refine the edge of the blister and also remains the rest part of the aluminum flat. Finally polish it with the mental polishing liquid. The final product