Japanese has functional elements with grammatical, semantic, or pragmatic functions. Case markers mark grammatical relations; the Q-particle clause-types the sentence as an interrogative; and the topic marker designates a phrase as the topic of the sentence. Along with these functions, we argue that these functional elements have a uniform function of assisting in the labeling of structures. There are two ways in which they do so. In one case, a functional element attaches to an item that cannot otherwise project to induce projection, an idea we base on Richards’s Contiguity Theory. In the other case, a functional element attaches to an item that is projectable but requires the projection to be blocked, allowing a sister item to project. The Q-particle is an example of a functional element that, when attached to an otherwise unprojectable C, induces the C to project. In contrast, case markers attach to XPs, which are inherently projectable, and block them from projecting, allowing the sister element to project, following Saito. The same goes for topic marking. Across languages, many functional elements have this role of assisting in the labeling of structures. The Q-particle in Japanese, which allows the C to project, is similar to agreement in Romance, in which the agreement morpheme on T induces the T to project without the need to move an element to the specifier. Case marking, which blocks projection of a XP, is similar to augment vowels in Bantu, and it is no accident that these vowels have a case-like distribution. Finally, we speculate on how case marking and movement, both functioning to allow the sister node to project, have common properties of blocking projection.