Introduce: A lot of people use small tape measure to have an error, think rule hook is loose is quality problem, actually this is 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 blade band. The front end of the blade hook supports the measuring object, and measure the inside diameter. The top of the blade hook is zero point, and the value is read vertically.
The second method is hook measurement. First, pull out the blade band, hook the measuring object with the blade hook, and measure the outside diameter. The inside of the blade hook is zero point, and read the value vertically.