For power resistors there are also ratings for the voltage between the resistor leads ( any of them) and the case if it is a metal case for cooling, and if there is a water cooling connection. Ceramic resistors also have a rating for hot and cold use, as when they are at full power dissipation they are no longer usable as insulated case resistors, the case must be considered as conductive as the ceramic can carry current if it is red hot. You often get them with a steel mounting, which must be connected to one lead in operation, or soldered to the board and isolated.