I thought Takitus post Perfect Alignment Every Time - The Fiducial Alignment Ruler (design in post) was very clever, but my magnets were too big.
So here is a bigger version with pressure fit magnets using Dan’s design Dan Acrylic Iris.svg.zip. Thanks Dan!
Snap Ruler.zip (42.8 KB)
My magnets were BYKES Technologies Neodymium Magnets N42 1/2 x 1/16 inch (0.502 x 0.063 inch actual). I purchased 100 from Amazon for $20. I double stacked them in the holes. After many sore fingers pressing them in, I found it easier using another piece of wood to press them in. They are really tight, but no glue!
I my first attempt was on Acrylic, but I cut the Glowforge snapmark instead of scoring it. This created a double image that snapmark could not recognize. I tried putting tape and paper behind it, I tired coloring the edges with marker, I tried filling it with my wife’s nail polish, but no luck. I could get it to recognize the snapmark with the nail polish, but the alignment was messed up. The takeaway, don’t cut snapmarks, only score them. Also be careful pressing on Acrylic (see pictures below).
I recut the design on wood and snapmark worked perfectly!