How can I keep the cast on big enough to slip a curtain rod in there? I was gonna cast on with 2 needles (phew, that's a doozey) but then how do I leave one of them in there when I start knitting?
What in the world are you trying to do?...Ok that sounded rude. I know this person...so its ok |:)
I would suggest knitting upside down. Sounds like drapes...so knit from the bottom up then you can knit the last row or do the cast off and slip in the rod as you do it.
What about making tabs to hang over the curtain rod rather than encasing the rod. If these are for drapes, I would be concerned about the weight of the yarn eventually stretching your material downward. Perhaps a dense stitch pattern or a sturdy yarn would remedy this. Good Luck