It is in effect, because if the tool only, it may cause an error.For example, charged the wrong idea in the wrong menu. If there is a related technology, everything would be easier, more precise.
It is effective because it uses the same hand, it may cause errors such as the wrong idea if you think money is everything related to technology, it is easier and more accurate.
I have to use the hand because if only it can cause error such as charge wrong, think the menu wrong. If technology involved everything will be easier. Precise .