"Like yarn size (check out the Craft Yarn Council page..)
yarn can be very fine (lace weight), fine (baby or fingering) medium (sports or DK) Medium (worsted) chunky, or bulky
-in guy terms, think of drill bits.. they come in size too!
and if you have a big drill bit, and drill a big pilot hole, you need a big screw or lag bolt to go along!"
Drill bits...I love it!!