This paper examines an aspect of the grammar-interaction interface with respect to how participants orient to intra-turn phrasal unit boundaries as a locus that has interactional import for turn and sequence organization in Korean conversation. Phrasal unit boundaries in Korean serve as a space within a turn in which the speaker of the turn in-progress invites the recipient to acknowledge the speaker's point expressed up-to-that-point and collaboratively display his/her understanding thereof. In a sequentially and topically 'ripe' context, such unit boundaries often constitute places where more active participation on the part of the recipient is invited in the form of collaborative completion in which the recipient co-constructs the primary speaker's on-going turn. Phrasal unit boundaries also provide interactional resources which the speaker may exploit to sequentially delete out a problem in talk, e.g., by a sort of tying operation in which a subsequently added phrasal unit ties back to the speaker's previous utterance to the effect that the intervening talk containing a problem is canceled out by way of being shown to have been an interruption of the speaker's turn in-progress. This practice points to an aspect of the way in which the 'agglutinative' grammatical process involving the use of phrasal units shapes interactional patterns as observed in the course of organizing turns/sequences and managing problems in talk.