| 摘要 |
The present invention relates to a plumb-bob and magnet combination for attachment to a beam. The plumb-bob and magnet combination for attachment to a beam includes a magnet having a top flat surface that is connected to the base, the magnet having two opposing sides that contain recesses, a hollow casing for encompassing a string of the plumb-bob and having a top surface slidable along the magnet, the hollow casing including lips on the top surface for sliding engagement with the recesses on the sides of the magnet, a lock on one of the lips of the casing and being cam operated by a lever that moves in the direction of an arc on the top surface of the casing for locking and unlocking the casing to the magnet, and a cantilever extending from the casing and having a free end with an aex from which the string hangs with a weight at the free end, the string being wound in the casing.
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