A homemade template can be used to mark walls for hole patterns before cutting.
TAKEN FROM THE CABLING INSTALLATION & MAINTENANCE ARCHIVES.
Problem
Inconsistent placement of communications outlets is common in cabling installation projects. Outlets are often installed at different heights than electrical outlets, and frequently the communications outlets themselves are at different heights. Another problem is that, if the installation is not done carefully, the outlets may not be level. Unlevel, inconsistently placed outlets are unsightly and can present a sloppy image in a work area.
Solution
Make and use a template to mark walls for hole patterns before you cut the holes into which communications outlets will be placed.
Procedure
1) Construct the template using a 2x2 piece of riser board, a 12-inch length of 2x8 wood, washers, bolts, wing nuts and a level. The diagram shows what a finished template should look like. Not shown in the diagram are several felt dots, which should be applied to the back of the 2x8.
2) When you need to install a communications outlet during a cabling installation, adjust the template to the desired height, or match the height of the existing outlet(s).