Trivet
Manhole Base Set-up
1. Prepare the laser for use: Attach handle/rod mount,
apply power, center the line adjustment, and enter
desired grade. Mount the height adjustable rod (center
the rod height in its adjustment range) to the trivet.
(Figure J)
2. Transfer elevation from the hub to the manhole base.
3. Position the trivet over the manhole center: Place the
front leg of the trivet on the centerline-of-pipe, 5” (13
cm) in front of the manhole center mark.
4. Secure the laser to the rod at the approximate
elevation where the pipe centerline will be.
5. Allow the unit to self-level.
6. Use the height adjustable rod to precisely adjust the
beam elevation. The centerline of beam marks on the
side of the unit are also convenient for establishing
elevation.
7. Align the beam to the forward manhole. Recheck all
the alignment steps to assure accuracy. Check that the
unit is level with an accurate grade setting. Proceed to
lay pipe.
Rod and Crossbrace System
1. Prepare the laser for use: Attach handle/rod mount, apply power, and center the line
adjustment.
2. Mount crossbrace inside the manhole, perpendicular to the centerline of pipe being laid.
Use the level vial on the crossbrace to position it level. Holding the two points firmly against
the manhole wall, extend and tighten the adjusting screw point against the opposite wall.
Tighten until the crossbrace is solid, with the points planted firmly into the concrete.
3. Secure alignment element to the crossbrace using the secure knob. Hang the alignment
element on the crossbrace so that the line control and front secure knobs face the forward
manhole. Measure manhole width where the crossbrace is mounted and use the center
as reference. Place the right edge of the alignment element 2 1/4” (57mm) left of manhole
center.
4. Slide the calibrated rod with the point attached through the alignment element, plumb it
using a hand level, then tighten the secure knob.
NOTE: Pull up on the crossbrace as you tighten the alignment element, then release after it
is tight. This places downward tension on the rod and increases its stability.
5. Establish invert elevation and beam height (see previous section on “Transfer of Elevation -
Special Transit Method”).
6. Secure the laser to the rod at the correct elevation and allow the unit to self-level.
7. Align beam to the forward manhole (see previous section on “Alignment – Special Transit
Method”). Recheck alignment steps to assure accuracy. Check for level unit and accurate
grade setting, then proceed to lay pipe.
15
Figure J
