Generally, we have to protect each conductor against overcurrent, and we have to do it at the point at which the conductor gets its voltage supply. The tap rules give us the ability to protect a conductor at the other end, the load end. That represents a degree of risk, since a fault in the middle of the run would not have any protection. To reduce the risk, in addition to providing physical protection for the conductor, the rules require that the overcurrent protection consist of a single overcurrent device. It can be the main breaker in a breaker panel, or the main fuse in a fuse panel, or an enclosed breaker, or a fused disconnect. But it can only be one such device. In other words, you don't get to use the "six handle rule" in a tap rule situation.