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Screws won’t bite into brickwork unless the hole is lined with a plug, and
the plug’s added pressure may split the brick in any case. But PA Fixings of
Essex has patented a screw that does away with the need for a plug—though
it’s not at all clear why it works (GB 2 344 629). The shank has several
threaded sections spaced out at intervals along it. Each section has three turns
of a thread. The two outer turns are the same size, but the middle one has a
larger diameter so it stands proud and bites deeper into the brick. You drill a
hole into the brick, and the screw taps itself—without, it is claimed,
making the brickwork crumble.