When I put a cardigan together, the sleeves are the last thing added and when I am darning in ends, I always keep the tails separate so the sleeve can be easily removed without too much trouble. It’s a chain stitch, so simple enough to unpick the last loop and pull it off. Undo the underarm seam – only need to go about halfway, so the sleeve will open out to rehang the same width of the needles as stitches at the underarm point – again when I was seaming this, I plan so the tail end is at the top of the underarm just for this event. Rip back the sleeve cap to the underarm and I want to shorten it by 10 rows so rip back another 8 rows. Hang the 10th row and pull out the 9th row that was holding the stitches and then rip out the tenth row so there are no split or partial stitches. Now, because the whole garment was already washed, I can’t reuse that yarn to make the sleeve cap again - the gauge won’t match but fortunately I have enough of the charcoal, new and unused! From the notes I made on my schematic, I know exactly what row I was on and how many stitches at the underarm point so this isn’t guesswork and if there was one or two decreases in those last ten rows, it’s not really going to effect the width of the sleeve enough to bother going further down and trying to re-shape to exactly what was there originally – the sleeve cap is the important part here and it worked fine so the new one will be the same. I will wash and dry all parts again (in the photo you can see the line where the new, unwashed yarn is but that will disappear with the next laundering) before reattaching the sleeves – actually the front bands are still unwashed at this point.
I don’t remember ever showing this little trick of mine for finishing the ends of a stockinette band like the new front bands. I take a long straight pin and thread it through the outside edge of the stitches, repeating with a second pin on the other side, to take the curl/roll out of the end. Then I steam this, so it lays relatively flat. With a tail of the yarn, beginning at the inside, stab stitch - don't whip stitch or back stitch - go in two stitches, through both layers, then go up and out the next two, staying in the centre of the outside row - neatly to sew up the end invisibly. Hope you can see this!