Buddy of mine tried this exact thing at his shop in Kentucky, swore by it for a month. Then one cold morning he got lazy, skipped wetting the ring, and spent the next three hours chipping a clinker the size of his fist off the firepot. He texted me a photo of that thing sitting on his anvil like a trophy. Next time I saw him he had a spray bottle mounted next to the forge, filled with water, just for that ring. He still forgets to use it half the time, but when he remembers, he's back to pulling clean coal out of the fire.

The 1/16th thing is actually the bigger issue than the crooked lines. Dollar store rulers are usually made from a cheap plastic mold that shrinks as it cools, so theyre rarely dead on. That tiny bit adds up fast when you're drawing 30 grid boxes across a page. I had a similar thing happen with a clear plastic ruler where the zero mark was set back a bit, so every measurement was short by about a millimeter. It was fine for quick sketches but terrible for anything where the lines actually had to meet up. Checking your ruler against a known straight edge or another ruler is a solid habit, but honestly the real fix is just spending a few bucks on a decent metal one. I keep the cheap ones for cutting mats now where precision doesn't matter.