It’s a good idea to cover the back, sides, and top of a glider cage while leaving the front open to interact with them.
A cage cover holds the gliders’ scent around them and dims the lights, making them more likely to come out and explore the cage.
A cage cover holds in their mess and helps funnel it into the drop pan.
Cage covers can be very pretty and match your cage theme. You can purchase cage covers from a number of very talented glider community vendors, or you can easily makeshift one with a large dark cut of fleece and three binder clips. It leaves a gap on top, so I stack spare fleece on my cages to cover that part.