a thread that you use for stringing beads that kind of frays at the end. It's elasticated but isn't 'Elasticity' as that doesn't fray. This thread was really easy to string and knot.
Do you have a picture of something similar to what you're describing Joanna? We might be able to help you a little more if we can see a picture of it- some things are quite hard to describe in words aren't they!