Weights

When I had my boa- the clips never worked for her, she would always push the top open (i always caught her she never got out) I also had weights on it.
The boa stayed with my ex, and I got a baby ball python right away when I moved and got the slide in top that has built in clips that snap in.
Most secure top I believe if that's the type of enclosure that you choose.

My clips have always worked just fine, but I also have a lazy snake who doesn't seem very interested in escaping. Bumps his nose against the top from time to time, but that is about it. But for the most part I'd say they are secure. They've managed to keep the snake in and the six year old out. Haha

Personally I don't like racks. I guess they are ok if you're breeding, but personally I like to see my snakes :D

I agree with the slide in top. Weights look goofy on top of the tanks :rofl::rofl:

I've used clips.