Many people use a small tape measure have a mistake, think that the ruler hook loose is a quality problem, in fact, this is a professional industrial design. There are two kinds of measuring methods for small tape measure, the first is the top measuring method, the second is the hook measuring method.
The first one is the overhead measurement. First, pull out the ruler band. The front end of the ruler hook supports the measuring object, and measure the inside diameter. The top of the ruler hook is zero point, and the value is read vertically.
The second method is hook measurement. First, pull out the ruler band, hook the measuring object with the ruler hook, and measure the outside diameter. The inside of the ruler hook is zero point, and read the value vertically.