PARAPET (Heb. מַעֲקֶה). Ancient roofs were flat and in general use (cf. Josh. 2:6; Judg. 16:27; I Sam. 9:25f; Isa. 22:1; et al.), and the Bible enjoins "when thou buildest a new house, then thou shalt make a parapet for thy roof, that thou bring not blood upon thy house, if any man fall from thence" (Deut. 22:8). The parapet must be not less than 10 handbreadths high and strong enough to keep a person who leans on it from falling (Sif. Deut. 229; Maim. Yad, Roẓe'aḤ 11:3). The law was given a far wider application, however, and made to include the need to remove any object that constitutes a public or a private hazard. Such precautions include fencing or covering a well or a pit (Maim. ibid., 11:4) and not keeping a savage dog or a shaky ladder in one's house (BK 15b). The statement of R. Eleazar (BK 4:9), that "No precaution is adequate [for a vicious ox] save the slaughterer's knife," is based by Abbaye on this same law (BK 46a). For the same reason one who keeps a wild dog or cat in his house is placed under the ban (Ket. 41b). Even if only the owner is endangered and he is willing to take the risk, he is forbidden and forcibly prevented if necessary (Maim. ibid., 4f.).