Most of the time just having the city turn the water on/off does work just fine. Problems is, there are times when you might need to cut the water immediately. For example, one time I was working in my basement near where the 1" supply line entered the house. There was a ball valve that the plumbers had installed 4 or 5 years before this when they installed the new pipe. I bumped my step ladder against the valve and the next thing I knew, the valve was completely off the pipe and I had water coming into my basement under 90 psi! I went to my meter box and discovered the rod to shut the water off had a rectangular end that required a special tool. I tried pipe wrenches and an adjustable wrench, but couldn't get enough leverage to turn the valve. I called the city and found the only one on duty was on a call on the other side of town. He came as quickly as he could, but you can imagine how much water I had collected by then. The next day, I had a welder friend make my a key. I have used it a couple of times when I had other problems. It's true the city usually doesn't want you to have a key, but I'll accept their wrath if I even get called on it, but if/when I have another emergency, I can deal with it.