Field guide · free
Printable crack-width card
Print this page at 100 % ("Actual size", not "Fit to page"), cut out the card and take it to viewings. Check the print first: a bank or ID card should cover the dashed outline exactly, and the rule should measure 100 mm.
- The thinnest bars (0.1 to 0.3 mm) may not print cleanly on every printer; treat them as a guide.
- On a phone screen the card is not to scale. Print it.
- Card stock or a laminated sheet lasts longer in a pocket.