I have to confess that I am guilty of making kilts and other folded items - English smocks for instance, out of anything that can be persuaded into a corrugated waveform - I use a one inch wide cotton tape to weight down the hem and also protect it from stress and fraying.

I normally buy it in white and dye it to the base colour of the kilt as required. I do sometimes come across odd rolls of coloured tape, I have black and khaki for instance, which I buy as it will always come in handy.