Thanks for your reply. How does it stand up to the wind? I don't have
any
grass or soil to put it on, so I have to put it on a paved concrete area,
but I can't figure out how to fasten it down so that it doesn't blow away.
Also, does it get mildew and mould?

my 4 shelf one I've tied to a fence by threading wire through a whole in the
plastic, going round the supports, then back to the fence. Each spring I
take off the plastic, screw it up and put it in the garage, each autumn it
comes back out. I've never cleaned it and never had any mould, mildew etc.
Hayley