Between 1500 and 1974, the entrance portal was barricaded by a solid wall, not an actual door. The popes themselves began the ritual destruction of these walls followed by masons who completed the actual task demolishing it. This describes a rite that has nearly always supplied the principal subject depicted upon the long series of Jubilee medals issued by the numerous Popes who have opened and closed the holy door at the beginning and end of each Jubilee year. Each of the four basilicas has its own holy door.