This a pic of a few of my breeding pens showing doors, I just framed from the 4x4s used for fencing. I use 2" heavy duty knotted netting can't remember right off hand where I ordered from it's been a good while. I will try to look it up for you.
I use a 2" knotted netting to topmost of my enclosers/pens, works well for me but there are a few steps you need to do if you're in heavy snow area. Pic for example.