The invention relates to a hasp which comprises a plug with an improved shape and aims at providing a hasp consisting of a protruding part formed on the clips of the plug, wherein the protruding part comprises three protruding faces protruding from three side faces of an arm. The hasp comprises the plug and a socket, the plug comprises a pair of clips, and each clip is provided with three protruding faces, and the socket is connected with the plug through accommodating the protruding faces of each clip formed on the plug, wherein the plug inserts into the socket.