| 摘要 |
A laser plumb device (10) comprising a facility (12) for emitting two narrow light beams (A) and (B) in which the light beams (A) and (B) are opposite and aligned to each other. A structure (14) is for supporting the light emitting facility (12) in a vertical position. When the supporting structure (14) is placed over a layout mark (16) upon a floor (18) under a ceiling (20) in a building (22), the light emitting facility (12) will cast the first narrow light beam (A) onto the layout mark (16) upon the floor (18) and will simultaneously cast the second narrow light beam (B) onto the ceiling (20) to transfer the layout mark (16) from the floor (18) to the ceiling (20).
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