Can someone point me to where I can find out how to replace screen for the top/ceiling portion (over the pool) of an aluminum framed pool enclosure? Sides are no problem.

Can someone point me to where I can find out how to replace screen for the top/ceiling portion (over the pool) of an aluminum framed pool enclosure? Sides are no problem.
When I had mine done... for the top screens they used a small guy that walked and moved around on some big planks of plywood that they moved from panel to panel.