| 摘要 |
A device for checking the verticality of a surface includes a plumb-bob attached to one end of a plumb-line, the opposite end of the plumb-line being attached to a case. The case has a through bore for the passage of the plumb-line and an external surface of the plumb-line is adapted to support the plumb-line wound on said external surface when the device is not in use. |
