Is there a standard amount that you're meant to press down? Like, until the measurement doesn't increase further, no matter how hard you push? I wonder what level of pressure is used when medical staff measure length. It would be difficult to standardize the level of pressure for scientific purposes, so perhaps they push down until it's impossible to gain another 0.1"? That would standardize the data to the nearest 0.1" and take out any errors in measuring.