How I Check Probe Calibration

This might seem obvious to some but I'm pretty simple minded. I check all my temp probes at least once a year. Couple years ago I grabbed a piece of scrap plywood and drilled a hole in it. I get a small pan of water up to a rolling boil, dial back the flame some to keep the radiant heat from the sides to a minimum, then lay this across the top. It fits fairly snug so you can control the depth of the probe tip. BTW, this probe was reading 30 degrees low when I first checked it.