How big are the holes in the mesh? It appears to be 1" which could be a problem if you have small gliders.

You really cannot "litter train" gliders. They can and will mark any surface in the cage. Gliders will pee & poo when and where they please.

What kind of litter are you trying to use. If they are in direct contact with the litter they could ingest it which could cause an intestinal blockage.

Hamsters naturally use one area in their cage - usually a corner - so yes they can be trained to use a litter container placed in their usual spot.

The holes in the mesh are about 1/3 inch or less, and my glider can't eaven fit their head's through the holes.

Yes, my glider's still use the restroom while they run around and play, but I've had quite a bit of progress getting them to go into the huge litter tray at the bottom of the cage. I've heard that some glider's don'r care for the bottom of the cage, however my glider's love to carry their food to the bottom and eat it there.

I'm not really using a "litter", I just lined the tray with about an inch of aspen shavings. (Which my vet says is the best for glider's next to newspaper.)

My glider's LOVE papaya, and rather then using it as dinner I use it as a treat. Everytime they go to the restroom in the tray, I give them a little bit' of papaya, and they've actually made quite a point by going to the restroom in the tray before I come to take them out of their cage.