[Uncle Billy]

Close the jaws and set the dial at zero. Then see how much pressure you can put on it at zero (fully closed) while still keeping it reading zero. Don't overdo it, just enough to get an idea how rigid the calipers are. Then when measuring anything, zero it first and use the same pressure to take a measurement, but no more than necessary. If the zero varies without much difference in how much pressure you're giving it, you need a more rigid instrument.