awesome find ! yes, thats a charcoal rail. usually there are two of them but i use only one at a time as i use the indirect method almost all the time. the hooked ends go over a grate rod on the charcoal side and the lower little elbows go over another grate rod and kinda locks in. you can move it in and out depending on the amount of coals you are using. i use that plus a piece of expanded sheet metal that is taller and a bit wider than the holder so i can pack in more coals for longer smokes.