Place the mirror against the wall in your desired position.
How To Hang A Mirror Flush Against The Wall. Using a pencil, mark around the top and bottom corners. Double check that the wall is flat.
How to Hang a Heavy Mirror Without Nails, Screws or ... from cdn.shopify.com
Use a level to ensure that the mirror will not hang remove the painter's tape from the wall. When placing the cleat, be sure to account for the part of the mirror that will be above it. It doesn't have to be!
Place the mirror against the wall in your desired position.
Another option is to lean the tall mirror against the wall. Hold the mirror against the wall again, making sure to line the top up with the mark you made earlier. When placing the cleat, be sure to account for the part of the mirror that will be above it. Drill a hole into the wall at each pencil.
