Abstract: A fastening device for releasably or non-releasably fastening free ends of two parts of a neck strap or crown jam of a halter to each other. Each of the two parts has one end fixedly connected to another part of the halter and one end free. A free end of one of the neck strap parts is connected to a buckle. The free end of the other neck strap part is formed of two overlapping straps. Both straps near their free ends contain a plurality of aligned holes, a selected pair of which are engageable by the buckle to non-releasably fasten the ends of the two parts of the neck strap or crown jam to each other. A two-section releasable fastener is attached to one of the surfaces of the two straps near its free end. The two sections are engaged with each other when the strap is passed through the buckle and folded back on itself. The engaged sections resist separation upon application of longitudinal tensile forces of ordinary value, but when the magnitude of any such force exceeds a predetermined value, they separate.