(one's) (hand)writing is like chicken scratch
One's handwriting is very poor, messy, and illegible, likened to the marks made in the dirt by a chicken. I can't understand these notes at all, your handwriting is like chicken scratch! Good luck reading that—the kid's handwriting is like chicken scratch. A: "What the heck does this letter from Jon say?" B: "I know, his handwriting is like chicken scratch."
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