Most table saw fences don’t come with a digital readout accurate to 0.001″. You can buy products that add this feature, but they can be expensive and they’ll only work on the tool on which you mount it. With Mag-Dro’s magnetic caliper base, you can take a 6″ caliper, a tool you probably already have in your shop, and turn it into a positioning tool.
According to Mag-Dro, the base works on almost any unpainted steel work surface, although I’m not sure why they say it has to be unpainted — if the magnet is strong enough a little paint shouldn’t bother it. It looks like you can quickly mount and unmount your caliper in the base by turning a friction knob.
Mag-Dro provides a tips and tricks PDF on their website that shows you how to use the caliper base and caliper to do things like align a table saw blade and fence, measure run-out, cut boards to an exact width, adjust a planer, and more. You can pick up Mag-Dro’s magnetic caliper base for $10 before shipping.