Yosef Karo, Translation:Shulchan Aruch — Orach Chaim 460…
“ Paragraph 4 - We do not make designs, like drawing the shape of an animal or a bird on the matzo. However, everything done with the comb so that it doesn't swell is permitted, as is putting holes in the matzos. In any event, one should hurry to make them and not leave them sitting. Rem"a: The matzos should be crackers, and not thick like other bread, because crackers do not rise quickly. ”
