If you're hanging a thermostat or similar device on a wall, you probably want to ensure that it's evenly lined up. One way to achieve this is to use masking tape.
Place a piece of masking tape horizontally on the back of the thermostat lining it up with the mounting holes. Take a pen or sharpie and create to "X" marks over each of the mounting holes.
Remove the masking tape from the back of the thermostat and using a level, tape it to where you intend to mount it on the wall.
Once you're satisfied with the placement, use a drill or hammer to create pilot holes at the marked locations on the tape and insert the nails or screws into the holes. From there, remove the masking tape from behind the nails or screws on the wall.
Finished! You've now evenly mounted your thermostat to your wall.