I sewed it myself, so the stitches are crooked.
Remember how 縫う means "to sew." Well the only way you can see if a pair of jeans has been sewed with your eye is if you see a seam. If your eyes can't spot the stitches, then it probably wasn't sewed at all. Maybe it was superglued together.
This is a combination of the words 縫う and 目. Both use the kun'yomi readings so just change the う to い and it's easy! You'll also see this word spelled 縫い目 too. They're exactly the same!