There are a few ways to cut mirrors, depending on the size and shape of the mirror. For small or simple shapes, a glass cutter can be used to score the mirror and then break it along the scored line. For larger or more complicated shapes, a wet saw may be used to cut the mirror. First, the desired shape is drawn on the mirror with a marker. Then, a straight edge is used to follow the lines of the drawing and create a cutting guide. The mirror is placed against this guide and then run through the wet saw like you would with any other piece of glass.