Originally Posted by
vane171
This interesting gizmo I take it you don't need to wrap around a pipe, it is enough to have access to just a part of the pipe's curved body, right?
No, it's a tape measure that you wrap around the object to be measured. The tape is offset (shaped like a "Z") and the scale on the main part of the tape and a Vernier scale on one end. This allows you to get a precision circumference. The circumference is marked in pi(3.14159) inches or centimeters, and so reads directly as diameter.