How can I screen in my patio? It is open on 2 sides and has a concrete floor. The other two sides are rock walls. How do you frame it and put the screen on? are there any variations in design or just a standard one? Thanks.

There are lots of variations. If you have a lowes or Home Depot nearby, check out the plastic "screening systems" that are popular these days. I'm sure they'll have literature that will show you what you can do. Then get a carpentry book that talks about porches. You should be able to find useful info at your local library.