Piping.
I've made piping before that was out of cotton, it was easy. Cut on the bias, jobs a good-un! But have you ever tried to make bias piping out of silk chiffon? I would recommend that you don’t bother! I tried to cut it on the bias and the fabric moved so much I ended up with a flouncy spiral!
So I decided to break the rules and make the piping out of a strip on the grain. It was hard and as i was stitching it, it was twisting round. I got to the end and realised my machine foot couldn't get close enough to the piping cord. I forgot I needed to use a zipper foot, which I don't have at home. So i took the plunge and hand stitched it close to the piping cord. Then i had to hand-hem it beforehand stitching it into the sleeve. Now I have arthritis!