It's a 3 ft length of threaded steel rod that ACE cut for me about 7 inches. I used 1/4 in nuts and washers to attach to the bottom grate and added just a nut and washer to hold up the top grate. I later added another nut to make is a little more steady. The reason for making the threaded rod a little bigger is that they can still be adjusted if I only have spares on or made bigger if I want to add a brisket or butt.
Thanks for the info. That gives me an idea of something to do for my Webers. I have a 22.5", and 18", and a 14". I may put together a system like that where I can make use of all of the grates. It'd be great to be able to pack a lot of chops or country style into the 22.5" when cooking for a large group.
Another option to try is a restaurant supply store and ask for a round 18" steamer stand. I went to one locally and picked one up for about $11 and will work about the same, except you will not have the ability to change the height.