| 摘要 |
PURPOSE:To readily position a laser emitting device by elongating a cross member provided on a trestle for the emitting device, and simultaneously contacting four contacting points of mounting angle specifying means with a cylindrical inner peripheral surface. CONSTITUTION:A placing base 8 for placing a laser emitting device 7 is coupled with a cross member 3 secured to the inner peripheral surface 2 of a manhole 1. Mounting angle specifying means 10 having a coupling plate 10a and four spikes 10b projected at the end side is provided at the end of a pair of threaded rods 3a of one end side of the member 3. When the ends 10c of the spike 10b of the means 10 at one end of the member 3 are simultaneously contacted with the inner peripheral surface 2 in the manhole 1, the member 3 is disposed on a plane perpendicularly crossing the axial center of the surface 2. The member 3 is extended in this state, the contacting portion 9 of the other end of the member 3 is contacted with the surface 2 to secure the member 3 on a plane perpendicular to the axial center of the surface 3. |
