GR translation: that dovetails inside you sharp as knives

[Mike Jing]

V676.37-677.1, P690.3-8   Which is why Slothrop now observes his coalition
with hopes for success and hopes for disaster about equally high (and no,
that doesn’t cancel out to apathy—it makes a loud dissonance that dovetails
inside you sharp as knives). It does annoy him that he can be so divided,
so perfectly unable to come down on one side or another.

What does "dovetail" mean here?