The ones I am looking for are early ones and were made with stone tips
and not iron. They used bows like you start fires with only much larger
and were drilled by Viking crews. These will be tapered, would have
rings because of the crudenes. They would vary in diameter and not all
be the same diameter as more modern holes woould be. Also, they would
not be a standard dimension like 3 inchs or 50 mm like a modern hole.
At least in Iceland they might be under a few feet of water if they
were early Viking as the sea level has gone up about a meter in 2000
years.
The reason Vikings more often used this type of mooring is that when
their men were gone being 'Vikings' the women and children were
vulnerable (but not as much as you might think). Lookouts were posted
on hills and when one reported an approaching ship then the women could
remove the poles that were in the holes and hide in their houses. That
is why the homes were partly underground and looked like small hills.
Then the passing ships would never know that there was a colony there.
A prime example of this is at Aux Meadows where the buildings were
purposely built near small hills so that they would blend in and be
totally hidden (unless someone walked out onto their roofs). The
buildings at Aux Meadows are inacurate reproductions and were not built
near other hills like the originals were nor did they make the roofs
with the correct pitch. They should be nearly flat and not steeply
sloped like those at Aux Meadows which were patterned after more recent
buildings. That was a warm period in history (the summer weather in
Iceland was about like England's is today but the winters were a bit
colder but not like they are today). It was such a mild climate in Aux
Meadows even that far north that it did not warrant making steep roofs
so that the little snow that fell would fall off.
Here is greater detail about how the Viking homes were hidden and photo
references.
It's very easy to see how a flat roof with dirt piled against the side
walls would make the reproductions of the Viking dwellings at L'anse
Aux Meadows (shown here
http://www.michael-thomann.com/nf/foto/bilder/antony1.jpg ) blend in
with the hillocks that dot the area (shown here
http://community.webshots.com/photo/162143049/1162239312012644958kqrZkw
) or be mistaken for a continuation of the row of hillocks in the
background of this photo (
http://community.webshots.com/user/weldonschloneger/2 ).
Here is a modern dwelling at L'anse Aux Meadows which when seen from
out at sea (the left side) is totally hidden. (shown here
http://artandcarol.ca/artandcarol/GNP5.jpg ). Be sure to check out
artandcarol.ca's outrageous web site full of photographs. I can't
recall when I have seen better photos and with them being outdoors I
like them particularly a lot.