So I was putting my new WSM together just now, it arrived about 40 minutes ago. I noticed that the top grill has 4 tabs that it sits on for support. Two of these tabs aren't long enough (the "tabs" im talking about are the tops of the grill straps I think they are called that screw to the side of the middle section).

This makes it really really easy for the grill to fall into the middle section! I would hate to have it happen with it loaded with food.

So tomorrow I'm taking it to my buddies house and having him weld on some 3/4" extension pieces for me so it holds it nice and secure, problem solved!

I wouldn't do that! If you ever decide to add a 3rd grate it won't fit! I would check at 12 and 6, 3 and 9 with a tape 1st. Adjust if needed or use 1/4" flat washers between the straps and middle section!

Ok, I guess I can hold off on welding it, it just sounded like fun!

I could also replace the stock bolts with ones a half inch longer so the grill would be protected from slipping down.

I'll figure something out.

Here is the 3rd grate mod I am talking about: http://img708.imageshack.us/g/img00095u.jpg/

25 cents worth of washers a fix it in about 5 minutes ! If its the normal problem with the WSM 18 ? There a bunch a threads here on what to do basicly you add a washer on each bracket and wala its fixed ! I don't own a 18 . But I have read many posts here on this fix simple and cheap .

Make sure the middle section is not out of round, this will also cause top rack to fall or sit unstable

After the washer fix, if it still bothers you that the grate might fall, you might try ...

... a couple of small C-clamps or window clamps to pinch the grate to the bracket tab or ...

... drill a small 1/8" pilot hole into the bracket tab and insert a #6/#8 1/2"~3/4" self-taping machine screw to form a vertical post.

You probably either have irregular parts, wrong hardware, or an out-of-round middle section. Personally, I'd try to determine which it is and try to rectify the problem without mods.