"tonyjeffs" wrote in message
oups.com...


The engineering bricks I'm using have 3 large holes straight through.

snip

AIUI; the three 'holes' are to permit heat to reach the interior of the clay
during the firing process.
Imagine a solid bick (prism); some parts of the interior are a long wasy
from the face. Old bricks had a frog - indentation- to achieve a similar
effect.

Thanks
Tony


--

Brian