This is a common water meter as found in the USA. Notice the white arrow. Just above it is the shut off valve. The photo is from Google Images. My meter is in a much deeper hole and the valve is much more difficult to reach for those times when I need to do a plumbing repair in the house and need the water to be "off." This Instructable will describe the water meter key I made from scraps welded together.
Step 1: What you can buy
This is a commercially available water meter key. They are not very expensive, but I have a welder and had some suitable scraps materials on hand.
Step 2: The working end of the key
The end of a commercial meter key is a "U" shaped piece welded onto a long rod. This photo from Google Images shows a commercially produced key on the shut off valve. Most commercial keys are painted black.
Step 3: My finished meter key from scraps
This is my finished key that I made from six short sections of various kinds of tubing plus the piece for the handle. The door knob gives you and idea of its length. Because our meter is deeper than usual, I needed a longer key than is usually found in the local hardware store.
A note on use of the water meter key: In our part of Idaho we have little rainfall. Our water for irrigating our lawns comes through a system of underground piping about 10 inches in diameter. It is fed by water in reservoirs from spring snow melt in the mountains. Once a week we open the valves in the backyard and flood the entire lawn with about 3 inches of water. The meter box fills with irrigation water and the shut off valve silts over so that it is not visible. My longer meter key is handy for poking around to find the shut off valve in the muddy silt.