This is a simple cardboard itomaki, or silk winder bobbin. I worked this out as a way to skein up tiny amounts of silk for embroidery skeins; it works well for times when you need a small but regular skein.
These pictures show the cardboard version next to the traditional Japanese version. The real thing is made from smooth-sanded but unfinished wood. The cardboard one is made from the back of a writing pad.
This is the basic layout to cut them out. I cut the pad back down a couple of times, so that I could get two bobbins - so these are 4 1/4" tall by 5" wide. First, measure the center from the sides, and draw a line.
Cut along either side of the line with strong scissors. It has to be 2 cuts, so that there is enough space for the two halves of the bobbin to slide together. The little curved piece comes out.
Here's the two halves.
This is how they go together.
And voila', the completed itomaki!
This is how it folds flat to pack.
This is the way to hold the bobbin and wind silk onto it. If you're winding raw silk, it's important not to lay a wet strand on top of another wet strand. It's not as much of an issue with dry silk. This is dry silk that I reeled with the Lao reel.
After a few more wraps, it starts to look more full. Keep up the pattern of working from one end to the other in a spiral, and it will all wind back off nicely.
If you're using the bobbin to make a skein, like for dyeing embroidery floss, you can flatten the bobbin to release the skein. If the skein has many yards, you'll want to tie it up first; if it's just a few, they will usually stay in decent order without the ties.