I took some pics of the channel system, but for some reason the website is not cooperating with me tonight. I can't get the pic to show up, and I've done this a million times before.
Anyway, a very easy way to get a tight fitting seal (gasket) between two pieces is to use silicone to caulk between the two pieces. When it dries, you have a rubbery, perfect fitting seal. I know, you're saying "but I don't want the sliding front stuck to the sides, why would I caulk the two pieces together?" You're right. That's why you take a piece of electrical tape and tape over the piece of glass you want to slide freely. Place the tape so that it will be over the area on the glass where you are going to caulk. Place the two pieces of glass in the position where they will be when you have the front shut. Caulk from both sides. Wait 24 hours and use a razor blade to separate the electrical tape from the sliding front piece of glass. Then peal the tape off of the caulking. You now have a custom made seal that will be tight enough to keep all of your fruit flies in the tank. If it's too tight of a seal, take a little sandpaper to it (it doesn't work extremely well, but it works!). That's an easy, cheap way to seal the gap you'll get with a sliding front terrarium. I'll try to post pics of the channel later.
-----
Homer W. Faucett III, esq.
Purveyor of Trivialities and Fine Nonsense