So, what is it?
They are hollow knitting needles with fitting caps. Also shown is a crochet needle that fits in the hollow knitting needle.
And why would you use it?
This model gives a solution to a strange problem I sometimes have: what should I take: knitting needles or a crochet hook. When I take knitting needles, I feel like crocheting. When I take a crochet hook, I feel like knitting. When I take both, I lose my crochet needle. When I take none of them, well, that won't happen.
The 3D model can be found in the last step.
If you like the idea, I would really appreciate a vote in the autodesk 123D contest.
Step 1: 123D design
The directions for the crochet needle are shown step 2/5
The directions for the hollow knitting needles are shown step 7/8
When you have done this, open a new file.