Denim is one of those yarns where I like the destination more than the journey, because it is so inelastic. Unfortunately, it also shrinks lengthwise, so one needs to knit about 10% more than the measuring tape indicates. And since, I am knitting a curtain, there will also need to be a bit extra for the sleeve for the rod.
This is going to be one heavy curtain. Linen (another inelastic yarn) would probably have been a better choice, but denim is what I had, so denim is what I knit.