With what may we cover and with what may we not cover? We may cover with fine dung or with fine sand, with lime or with potsherds, or with a brick or with the cover [of a cask] that were crushed. But we may not cover with the coarse dung, with coarse sand, or with a brick or with the cover [of a cask] that were not crushed, neither may he invert a vessel over it. Rabban Shimon ben Gamliel stated a general rule: Whatever makes plants grow may be used for covering, but what does not make plants grow may not be used for covering.