I've often heard the adage, "Measure twice, cut once" but it doesn't seem to apply to me. I have the unique ability to measure something two hundred times and still mess it up. Very frustrating, especially when cutting holes in something bulky like drywall. Messing up costs money! Luckily, Blind Mark of Michigan has devised an easy solution that even I can figure out for for cutting electrical-box access holes. Using a combination of magnets to locate the electrical box's position, the Blind Mark Locator shows just where to cut in two steps. After the standard blue or gray electrical box is installed, you fit it with one of Blind Mark's "targets". Once the wallboard or paneling is up, you use the magnetic "locator" to find the box and clamp onto the face, giving you a perfect guide for cutting out your box. It's a foolproof way to save yourself some mistakes and money. Blind Mark is available online for just $29.95.
lol.....or u can mark the floor and save urself the 30 bucks
For the most part proffesional drywallers dont mark plugs on the drywall before installing, they mark the floor, infact they will go aroung the entire project before they even start installing and mark all the plugs
if ur floor is already finnished us green painters tape,
-lay a peice of tape on the floor inline with the center of the plug outlet or switch
-measure up from the tape to the center of the plug
-write the measurement on the tape
-install drywall with minimall screws/nails(avoid fastening area sorounding plug)
-hold tapemeasure on green tape and measure strait up from floor make a mark on the drywall at ur prerecorded measurement.
CUT OUT WITH A SMALL ROUTER
-plung router bit throug drywall at center of plug
-move router bit utill edje of plug is detected the pull bit out just enough to move to the outside of the plug
-cut in a counter clockwise motion, this will hold ur bit tight to the plug and make it alot easeyer for that PERFECT CUT!