On Sat, 22 May 2010 16:30:35 +0100,
wrote:

what are plugged drainholes ?

A contradiction in terms?

Maybe they mean holes that are plugged to stop wind blown rain being
driven up and in through and open hole but the plug is soft rubber
with a slit in it such that water inside will seep out by capillary
action and as it evaporates from the outside draw the rest of the
water through.

--
Cheers
Dave.