Stretch magic is from Pepperell Braiding Co. They have these tying instructions: As this product is mostly used in home-jewlery making you will have to ignore references to beads.
Same kind of knot you would tie if you were winding single denier thread or fishing line. Good luck!
Stretch Magic Knot Tying Instructions:
It may be easiest to keep on end of the cord attached to the spool, until all of the beads have been strung. If you cut a length of Stretch Magic off of the spool, you may want to attach an alligator clip to one end, so the beads do not fall off.
First stretch the length of cord you will be using. This will help keep the cord loose.
String all of your beads onto the line, and cut it away from the spool, leaving at least 3 inches extra, on each end.
Make a half knot and then gently pull the two loose ends, to secure the knot.
Make the other half knot (forming a square knot,) and gently pull the loose ends together.
Repeat steps 4 and 5, producing four tight knots.
Using scissors, clip off the two ends. Be sure to leave at least 1/8- 1/4 inch to keep the knot secure. If you cut too close to the knot, the Stretch Magic could unravel.