I was on a plane (nothing new there) and just finished knitting the first of a new pair of mitts. These are a replacement for the ones that I had last year that I lost when I left them in a taxi. I wanted to make sure it fitted before starting the other one so I wanted to sew it up. All I had was the needle that I had made it on. So what to do? Adapt a 3 needle cast off.
I left the last stitch of the cast off on the right needle and put the left needle through the edge stitches of the first stitch. I knitted them together and then lifted the last stitch of the cast off over as you would normally, I then picked up the next 2 edge stitches and continued in that fashion. I am really impressed with the result. the seam is very neat and even with the amount of stretch required on mitts it looks good with the cast off side facing out.