Drill carefully, then install bolts
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Photo 1: Mark locations carefully
Mark the hole
drill 3/8-in. holes
fiberglass. For a
hole, use a
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Brad point bit
A brad point bit cuts a clean, sharp hole exactly where you want it without chipping, tearing, or wandering.
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Photo 2: Insert the bolts
Run a light bead of silicone caulk around the holes and insert the toggle bolts.
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Photo 3: Tighten the bolts
Tighten the toggle bolts. Hold the mounting bracket away from the wall as you turn the screws; otherwise the toggle will simply spin inside the wall.
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Use a brass screw for the toggle bolt rather than steel to avoid rust.
Fastening towel bars, shelves or hooks to a
fiberglass or plastic shower surround can be
tricky. The surround is simply too thin to hold
screws and there's often a gap of 1 in. or more
between the surround and the wall studs
behind it. But with 1/8-in. toggle bolts, you can
mount most light-duty hardware (like the
adjustable showerhead bar shown here). Keep
in mind that this leaves big holes (3/8 in.) in
the surround that can't be patched later, so
anything you mount will have to stay there permanently.
The mounting system shown here
isn't strong enough to support the full weight
of a person, so we don't recommend it for
installing safety grab bars.
Photos 1 – 3 show how to use 1/8-in. toggle
bolts in a surround. Everything you need is
available at home centers and hardware stores.
Here are some pointers:
- Some areas of a fiberglass surround may be
reinforced with plywood. After you mark the
hole locations (Photo 1), drill 3/16-in. holes.
If you strike plywood behind the fiberglass,
you can drive in stainless steel screws instead
of using toggle bolts. If you don't hit plywood,
drill 3/8-in. holes.
- When you're drilling through the side of the
surround where the shower valve is mounted,
apply only light pressure as you drill.
Otherwise, you might suddenly punch
through the surround and puncture pipes.
- When you buy toggle bolts, also
buy brass machine screws to replace the
steel screws that come with the toggles. Steel
heads will rust and stain the surround.
- When you tighten the toggle bolts (Photo 3),
it's OK to use a drill. But do the final tightening
by hand. Too much torque can crack