Many Weber Smokey Mountain Cooker owners like to measure the temperature of the cooker and the meat inside using probe thermometers like the Maverick ET-733 or using an automatic temperature control system. The trick is how to get the probe wires into the cooker.
One of the more popular solutions to this problem seems to be cutting a slot for the wires in the middle cooking section. Using a 4.5" angle grinder and a 3/16" - 1/4" grinding wheel, cut a slot starting at the top edge of the middle cooking section, through the lip where the lid rests, and just barely past the lip to accommodate the probe wires. You want to see a little hole below the lip when the lid is in place. Better to cut the slot too short, check the fit of the wires, and have to lengthen it than to cut it too long in your first pass.
Some people have used a Dremel tool to cut a slot, but the thin cutting wheel may require two passes to make a slot wide enough for the probe wires. Some people like to mask the edges of the slot with one or two layers of blue painter's tape before cutting. If you think that will help you, go for it, but many people skip the tape and go straight to grinding with good results.
You can cut the slot a bit deeper depending on the number and thickness of probe wires you intend to feed into the cooker. As you can see in the photo on the right, by making the slot just a little deeper you can easily accommodate three probe wires under the edge of the lid.
There is no need to paint the slot to prevent rusting. The slot gets coated with grease and smoke quickly and no one complains about rust developing in or around the slot.
It does take some courage to take a grinder to your precious Weber Smokey Mountain Cooker, but this modification is highly recommended by those who have done it.
thermometer slot photo: 2013 by Chad Bman