The "bishop" does not refer to a priest, but rather to a war elephant; consequently, the piece is formed like the elephant's trunk, and the slash serves as the aperture. You're referring to the hat worn by the Bishop of the Roman Catholic Church, which is known as a "mitre"... although the word itself means "crown" or "cap". The mitre was originally designed as a headdress for the Pope, but since then it has become customary for other bishops to wear them as well. Bishops do not cut themselves when consecrating a church because they are surrounded by their priests. They do, however, wear special clothing that includes a sword and cape for ceremonial purposes. These items don't include any blade that could be used as a weapon, so there's no need for them to be sharp. When the bishop prays over a church building before consecrating it, he often makes the sign of the cross with his hand held upright (like an elephant's trunk). No knife is needed for this action. Consecration is a ritual act in which a bishop transfers the rights and powers associated with the office of pope to another person. It can only be done while the other person is alive, and is usually done during mass. If anything happens to the bishop before he dies, then another person has to be consecrated in his place so that the office of pope cannot be suspended.