I bit off-topic, but I’d like to give a plug for high accuracy measuring devices.
I use a Leica Distro Last Tape Measure to locate my Martin-Logan speakers in the room to within 1/8-1/16 of an inch from the back and side walls.
I then use a digital level (Swanson Tool Co SVT200 9 Inch Savage Digital Magnetic Aluminum Billet Torpedo Level) to get the vertical "cant" of the speakers equal to within 0.1% of a degree (I prefer bolt upright).
Both of these make a audible difference, are one-time purchases, and are generally useful around the house.
-docknow