All right, let's zoom in on the end of this play—and by that we mean the last two lines...
COUNTY ATTORNEY: [facetiously]: Well, Henry, at least we found out that she was not going to quilt it. She was going to—what is it you call it, ladies?
MRS. HALE: [her hand against her pocket]: We call it—knot it, Mr. Henderson. (150-151)
If all we read of Trifles were those last lines, we'd probably say to ourselves, "It's about quilting? No thanks." But we've read everything that leads up to this moment. So we can see all the intense stuff that's bubbling under the surface of these deceptively simple lines.
First of all, this is a big moment of rebellion for not only Mrs. Hale, but also Mrs. Peters. The thing that Mrs. Hale is hiding in her pocket is the dead canary: the evidence the County Attorney needs to convict Mrs. Wright of murder. Mrs. Hale and Mrs. Peters are totally in cahoots here, and by not handing over the evidence both ladies are sticking it to the big bad male-dominated society that's been keeping them down.
No, it's not a huge act. They aren't leading armies of disgruntled housewives on a rampage across the country, but they are breaking the law by obstructing justice. They're protecting their fellow woman Mrs. Wright from a system of laws created by men.
This moment of unity is symbolized by all this quilt talk. Notice that the stage directions say that the Attorney asks about the quilt "facetiously," meaning that he's being sarcastic about it (151). He is essentially saying, "Haha, all we figured out is this stupid woman stuff that doesn't matter at all." This is, of course, dripping with dramatic irony. We know and the ladies know that it was the ladies' concern about "stupid girl stuff" like Mrs. Wright's quilt scraps that lead them to solve the mystery by finding the bird.
Also, don't miss the moment of pitch black humor at the tail end of the play. Mrs. Hale says that Mrs. Wright was going to finish the quilt by knotting it, which is a whole lot like the way she finished off her husband… by knotting a rope around his neck. The pronoun "we" also packs a punch in the last line. Mrs. Hale says, "We call it—knot it, Mr. Henderson,"which not only aligns her with Mrs. Wright and Mrs. Peters; it aligns her with every woman out there in the world (151).