Yosef Karo, Shulchan Aruch — Yoreh Deah 12 Not shechting into a pit
“ Seif 1 We do not shecht into a depression even indoors. If he doesn't want to soil his house with blood, he makes an ramp outside the pit and shechts there, so the blood flows down to the pit. But in the open market don't do this. ”
