Just plain old regular George,
Is there some sort of mark at the center of the box? How do you get that exactly right?
Most times yes, you have to remember I almost never see plastic nail on boxes.
Here is the most common box and bracket we use.
The bracket has a > notch right on center.
Here is another way we mount.
In this case the bar gets mounted 18" AFF to center and the boxes get screwed to the bar.
Here I used the bar as the specifications gave a finish measurement of 2" between the voice / data plate and the receptacle plate.
[This message has been edited by iwire (edited 09-05-2005).]