Thermoquad........Ok AJ, WHAT NOW?
The T slot. Above the idle mixture screw holes, where the holes exit in the t/bore. The slot is usually just above those holes. A rectangular slot, varies depending on carb but often 0.025 to 0.035" wide & 3/16" to 1/4" in height. They are part of the idle cct.
With the engine idling at the desired idle speed, ideally you want 0.020-0.040" of slot exposed below the blades. This is what is meant by 'T slot exposure', the amount below the blades.
More or less than this can cause flat spots, rich idle etc.
Hope this explains it.