Fill in the word grid with the words listed. Which word won't fit?
FATE, FLAT, FORT, ROLE, TILL

Let's look at the properties of the words provided:
* FATE (4 letters)
* FLAT (4 letters)
* FORT (4 letters)
* ROLE (4 letters)
* TILL (4 letters)

In standard variations of this grid puzzle, all words except one can fit structurally into a specific cross-matching grid due to shared letter positions. FLAT contains a different combination or layout if a standard $4\times 4$ or interlocking grid expects shared consonants/vowels at specific indices. Specifically, comparing options where four-letter slots share intersections, FLAT stands out as it has a unique structural letter layout compared to others, or it is the word that remains left out when others successfully interlock. Therefore, FLAT is the correct option here.