My father lays tiles for a living and he always did the same in metric, if he didn’t had something to measure things with him (which any professional should!)

A meter is basically a slightly longer step. I think most tradesmen over here got a pretty good sense how to walk a meter.

0.1m or 1dm or 10cm or 100mm is basically the width of your hand.

1cm or 10mm is roundabout the width of the pinky finger