Panels are hard to slip in roof area of unit, they seem to blow out in high wind on one side.  If you get a lot of wet heavy snow just watch out it pushes roof panels in.  I had to support the center part of panels to help with this issue.  Wish they could send me 3 new roof panels since they got wrecked during this winter ad early spring.  I only had unit a year.Though for growing plants when panels stay in the greenhouse with heat grows plants great all winter and early spring, then it gets too hot to grow anything.  I think the panels need more roof and side support and some good glue.  For the price it does what it needs to do, but I thought it came with stainless steel nuts and bolts so they looked like it, but, they are now rusting inside.  So the only thing that can rust is base and screws.  Aluminum will not rust.