Sleeve

"Sleeve" covers a lot of genuinely different construction problems depending on which type you're drafting. A set-in sleeve is cut separately and sewn into a curved armhole (armscye) after the body is assembled — the most common construction, but also the fussiest, because the sleeve cap has to be eased into an armhole that's slightly smaller than it is without puckering. A raglan sleeve extends in one piece up to the neckline, replacing the shoulder seam entirely with a diagonal one — easier to sew and to fit, which is why it shows up so often in beginner-friendly patterns and sportswear. A kimono or dolman sleeve is cut as one piece with the bodice, no separate seam at all, trading ease of construction for reduced arm mobility.

Set-in sleeve ease is the thing that trips people up longest. The sleeve cap is drafted with slightly more fabric than the armhole it goes into on purpose — that extra ease is what lets the sleeve stand up and round over the shoulder rather than collapsing flat. Two rows of easing stitches along the cap, pulled up gently before pinning, let you distribute that extra fabric evenly around the curve without a single hard pucker.

My honest advice for anyone learning sleeves: master a set-in sleeve on a forgiving fabric before you try it on anything precious. It's a genuinely different skill from flat construction, and the first few will be lumpy no matter how carefully you read the instructions.