Attention greenhouse builders. If boards are painted, sand off any slivers or dirt trapped in paint that create a rough surface. We recomend galvanised nuts and bolts over bright plated bolts which may rust after a year due to acidic nature of wood. Expanded polyethylene foam makes an excellent pad for covering the joints to protect the cover from chafing. This inexpensive closed cell foam is available from shippers supply companies and will not absorb moisture.
Carpet also works.