四分律刪繁補闕行事鈔 3.128

3.128

一者籬牆不周淨。《四分》云：半有籬障；多無籬障；都無籬障，謂露地也。非儲積相，故開之（必三面有院，開一面者，攝食義彊，亦同有罪。厨舍孤立，有院同之）。垣、牆、塹、柵亦如是（並非牆得周匝，隨共成相）。

The first is purity due to incomplete fencing or walls: The Dharmaguptaka Vinaya states: having half a fence or barrier; mostly lacking a fence or barrier; entirely lacking a fence or barrier, meaning the open air. This is not the mark of accumulating storage, so it is permitted. (If it has a courtyard enclosed on three sides and open on one side, its implication of containing food is strong, and likewise entails an offense. An isolated kitchen building with a courtyard is the same.) Mud walls, brick walls, moats, and palisades are also like this (all being cases where walls do not encompass the perimeter, but jointly form an appearance).