I was helping my Father on a big job in Los Angeles, a School so Union... and the Electricians roughed in all their work after it was framed. The next day the Dry Wall guys came in and covered the walls... covered the electrical boxes and everything. The next day the Electricians came back and took their hammers and started in a corner and going all around the room banged holes 16 inches off the floor and 4 feet off the floor...something like that, and revealed all their electric boxes and switches. All the way around these huge rooms.