This paper explores what makes successful unification of the two sub-elements of the preceding two conjunct clauses in the course of building the RNRed element via External Remerge that I have developed in my previous papers (Park (2010a-c)). In this paper I first show that what matters for the successful unification of them is not just form but syntactic identity which includes both strict and sloppy identity. In this regard, the union operation that is proposed for the unification is a syntactic operation sensitive not to PF but syntactic identity. I also show that the overt and the covert coordinating conjunction play different roles in distinguishing two types of the RNTed element: the one with respective reading and the other with cumulative reading. I finally show how ER, the union and the adjunction operations interact to add relational adjectives such as different and same to the RNRed element built in syntax. (Dongguk University)