On Sat, 21 Jan 2006 14:02:58 -0000, "John Rowland"
wrote:

A solution
could be to give the different styles of bollard different asymmetrical
shapes at the bottom, with matching differently shaped metal frames set into
the concrete - then it would be impossible to switch them or put them in the
right hole the wrong way around.

Ask a bollard-installer if that's a solution :-) Or ask the
storekeeper who has to stock 15 types of bollard-base. All of which
will become obsolete NEXT time some wally has a bright idea.