This paper explores phrase structure building of adjuncts. We propose that adjuncts have no labels ('Unlabeled Adjunct') due to inapplicability of the Labeling Algorithm (LA; Chomsky 2008) to {XP,YP} generated by External Merge (EM), but they can be labeled ('Labeled Adjunct') via Feature Sharing (FS; Chomsky 2013). Specifically, given a natural assumption on Narrow Syntax that Merge targets labeled nodes only (Chomsky 2000), derivations including Unlabeled Adjunct inevitably result in a "two-peaked" structure (Epstein, Kitahara, and Seely (EKS) 2012), while ones with Labeled Adjunct result in a "one-peaked" structure. It will be shown that the proposed analysis is theoretically desirable in that it can possibly eliminate adjunct-specific stipulations like Pair-Merge from syntax.