Faster is not always better , eyeballing it is faster.
But eyeballing is not accurate.
Why would a hammer be faster to measure with?
Because it's already in your hand, it never has to leave. You don't have to deal with a 3rd object.
One simple motion is all it takes, tap the hammer to the bottom plate and the box to the butt of the hammer and swing. It takes about a second from start to hammering the nail. The hammer stays in your hand as you move to the next box, you don't have to fumble with a block of wood.
Measure with a screw driver it would still take the same amount of time.The item you use to measure has nothing to do with the speed of the measurement.
I disagree, when the item you measure with is in your hand, it is much faster than using a 3rd item, like a black of wood or a screwdriver.
What I look at is consistant box hieght with a hammer you must move your measuring device (hammer) that allows for the real possibility of the box moving creating inconsistant height.
Incorrect. If you can't hold the box against the stud without it moving, you shouldn't be allowed to do electrical work.
With a 2x4 it stays in place during the nailing process thereby giving a greater probability of a consistant height.
This is what we call a "crutch", this is something I would expect from a 1st year helper who hasn't come into his own yet. It is unnecessary when dealing with experienced workers and adds to the installation time.