Help sewing in sleeves!

Hi everyone! I’m new to the forum and a relatively new knitter - I started in May during lockdown as a way to challenge myself to learn something new and I’ve really taken to it!
I am currently knitting a jumper as a Christmas present for my sister from the Harry Potter Knitting Magic book. I have completed the front and back and have connected the shoulders.
The pattern when knitting the sleeves almost before the end states “PM each end of last row for armhole placement. Cont even for 11/4inches” . I have done this and finished the piece and cast off all stitches as instructed.
In Making Up it just says “sew in sleeves. Sew sides and sleeve seams”
My question is - what are the PMs for? I have watched some tutorials for sewing in arms and none of them mention place markers? Any help is appreciated!

Welcome to KH!
It may be that the front and back have a notch where the underarms are bound off before working the shoulders. If the sleeves have markers placed at 1 1/4" from the end, that 1 1/4 slots into the notch at the underarm. The bind off at the top of the sleeve is seamed to the armhole opening and the side of the sleeve is seamed to the notch for about 1 1/4".

Ohhh!! That makes so much sense! Thank you so much for the clear explanation and the drawing! :smile: