A small ashtray - the cigarette notch keeps the soldering iron from rolling around.
The soldering iron is a Weller SP23 - I tried it with a cheap iron, but it burned up the coil after about an hour, right during it's first run. The Weller uses a different design heating element (I believe it's a ceramic in the weller versus the cheap wire-wounds) that holds up quite well to being left on for 2-3 hours at a time.
The other photo shows how the can is cut, just fill it with chips, push the flap sort of closed and stuff the iron into the hole. Just avoid having the neck of the iron body touching the can or it will melt/warp a bit.
The flavor results that I like best for the cheeses have typically been with alder, but any smoking chips can be used. No soaking of the chips, just straight from the bag into the can, and close all vents on the grill or Q or whatever you're smoking in - I just happened to have a spare 18" weber that wasn't doing anything, some guy in the UK has a video on youtube of him using a large tupperware container, a plastic rack and a coffee cup with the iron just dropped straight into the cup of chips. Anyway... I've found that 8oz blocks of cheese work well and one to two hours smoking time achieves my desired results. There is a color change, but nothing significant like what is seen on the typical commercial cheeses.
I think it was Kevin (SavorTheStick) who gave me the original idea for this setup.