"George Patterson" wrote in message news:P3EFh.4222$854.1160@trnddc04...
Pszemol wrote:

I know my English is not perfect, but what the hell you call plenum? :-)

Do a search for "Joubert plenum."

Plenum is an empty space UNDER the sand, so I am not sure
how can you understand the advice on vacuuming it...