Invert Set-up
Position the legs the same as you would if setting up
inside the pipe. Place the laser in the invert and complete
the set-up as shown in the Manhole Base Set-up in the
previous section.
Open Cut Set-up
When using the height adjustable legs in an open cut,
a stable base such as a concrete block, brick, or board
must be placed in the cut at the manhole center and
marked. This is best done when transferring elevation
(see page 10).
Place one of the blocks at manhole center. The front
leg will be positioned on this block 2” (5 cm) in front of
the center mark for critical high accuracy, or on top of
a centerline hub for most applications. Place the other
blocks, etc. so that they provide support for the rear legs
(Figure I).
Set up the unit for laying pipe as described in Manhole
Base Setup in the previous section.
Invert Peg Set-up (Open Cut)
This method is commonly used in open ditches. The cut
should be excavated approximately 6” (150mm) below
invert elevation. (Figure I)
1. Place a stake at the invert elevation.
2. Prepare the laser for use: apply power, center the line
adjust range, and enter the desired grade. Attach the
leg set with the centerline leg at the front and two side
legs at the rear.
3. Set the front centerline leg for correct pipe size using
the marks on the legs.
4. Place the laser in the trench with the single front leg
on the stake (peg). Rest the rear legs on blocks, bricks,
or the ground.
6. Align the beam to the forward manhole.
7. Recheck for accurate grade settings and a level unit.
Proceed to lay pipe.
NOTE: In open cut set-ups the optional long leg set is
usually required.
14
Beam Centerline
Manhole
Invert Elevation
Figure I
