On May 9, 7:15*am, "charlie"
wrote:
what would the adhesive do attaching the cleat to drywall? the paper isn't
very strong, and that's all you're gluing to.

One important advantage is that a fixed item doesn't
pry up its fasteners one at a time as it flexes. I've
used construction adhesive and masking paper to
make a tight conformation of a cleat to a wall: tape up
the masking paper to protect the wall, put down a bead
of glue on the cleat, affix the cleat over the paper,
then trim any paper away when it's dry. It's easier
than coping an oak board to a plaster wall...
With all the gaps filled, the board and wall move together.

Wood around screw threads can crumble with shock: glue can be
strong enough (a mantle cleat can have square feet of
glue area) to hold normal loads, then when a shock comes
along the screws get only a momentary load. The screws
could work loose under sustained load, we all see this
in doors with poorly mortised hinges. OK, it is a small
effect, but wood DOES give way under sustained stress
that a strong metal screw is likely to apply.


It's advantageous, where possible, to use large contact areas
where wood is stressed; a lap joint with dowels holds more
shear than the same joint with screws, because the dowel
surface area in contact with the wood is much larger than the screw
cross-section.