Re: Charcoal Screens
They are used instead of foil. Some people swear by them, some don't. You simply place the screen on the top of the bowl instead of foil, and hook the little "tabs" down to keep it in place.
I've used screens before, and I'll use them, but prefer foil. Here's some pros and cons.
Pros: so simple a 2 yr old could set it up, easy to clean, useful for many sessions before you need to get more, about the same price as foil in the long run, faster to set up than foil
Cons: very large holes, ash (and bit of coal if you're not careful) sometimes falls through, heat management becomes more of an issue, can sometimes add a weird taste, don't fit all bowls, cannot be used with all bowls, single unchangeable hole pattern
Really it's up to the smoker on preference. One of my friends won't ever use foil again, while I'd rather use foil and keep a screen in the bag in case I run out and Walmart's closed.