I put a wet towel over 2/3 of the screen. You may need to get it quite wet. This is okay because the towel is rather absorbent and the screen acts as a barrier (due to surface tension), stopping the water from dripping into the tank (you would have to be reasonable with how much water you use). I use a black towel folded to fit the top exactly (without any over hang). This can be an attractive way to set up a glass enclosure with a screen top.
Keep in mind, this is okay if you do not have a butt load of snakes. Mainly because you have to wet it every 2-3 days and wash the towel every week (preventing build up of bacteria). Having said that, I think this would only work (even if you only have one snake) if you were willing to take the time (10 minutes every couple of days and the time to do a load of laundry) the snake needs/deserves to properly set up a visual enclosure.
There is also the option of buying a PVC enclosure with a clear front for viewing. This is a more expensive route to take but it sure does look great.
I know there are a lot of people who have MANY snakes on this site and it makes sense for them to use tubs/racks. However, there is a niche group of people looking for information on how to successfully set up display enclosures to show their pets off. Lets use the collective knowledge of snake husbandry, and help us out.
Jimmy
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