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Components
Vise Grip 18SP clamp (modified)
Assembly
To assemble, slide one Magnet block onto each of the
clamp's two pressure feet from the side (Fig. 1). The
magnet and pressure foot will be mutually attracted
and will snap into place when fully inserted. The Mag-
net blocks can be rotated on the pressure feet. To
remove, rotate as in Fig. 1, pull to separate pressure
foot from magnet, and slide off.
Instructions for use
Two-person operation is recommended, but one per-
son working below and above the roof deck may
complete the task. For two-person operation, hands-
free mobile communication may aid in coordination.
Below the roof: configure and place Magnet blocks
WARNING:
Climbing on ladders and working in confined spaces are
hazardous activities. This tool should be used only by people trained and
experienced in workplace safety compliance, including fall protection,
personal protective equipment use and other hazard mitigation practices.
Rotate both Magnet blocks to the same orientation. Positioning with slots
down (Figure 2) is recommended for a stronger, easier-to-find magnetic field
on the rooftop. However, a slots-up (Figure 3) orientation, while offering a
weaker magnetic field, provides greater reading accuracy when no insulation is
present and roof deck and membranes are less than one inch thick.
Magnet blocks (2)
Compass block
Figure 1. Assembly
3
With clamp open, slide Mag-
net blocks upward with one
on each side of rafter until
the full length of each mag-
net block is touching the
bottom of the roof deck at
the target location. Squeeze
clamp handle to hold in
place. If necessary, adjust
clamp tightness so that
Magnet blocks stay in place
when clamped. CAUTION:
Figure 2. Slots down
Do not overtighten clamp;
excessive pressure may dam-
age Magnet block internal components.
Make sure both Magnet blocks are touching the roof deck or are the same dis-
tance from and parallel to it, and that they are tight against the rafter. If the
clamp does not allow Magnet blocks to reach the bottom of the roof deck, they
may be clamped as close as possible to the deck, assuring that the magnet
blocks are oriented parallel to the deck, or they may be removed from the
clamp and held manually on both sides of rafter against the deck.
Avoid working near any large ferrous metal object, which may distort the mag-
netic field and result in an inaccurate reading.
After the center has been located and marked on the rooftop, move Magnet
blocks to next target location.
Above roof: locate rafter center
WARNING:
Working on a roof is hazardous and can be fatal to yourself
and others. Do not work on a roof unless you are trained and equipped to
do so safely and in compliance with all applicable laws and regulations.
From a safe position on the roof surface below or above the target position,
hold the Compass block with one of its long, narrow sides against the roof sur-
face (Fig. 4). Do not hold it in the flat orientation, as you would if using the
compass to locate earth's magnetic north. Doing so will cause the compass
Figure 3. Slots up
(greater precision)
(stronger field)
4
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