Not sure if I remember right, but I believe they use a small washer that fits just inside the pole and is stopped by the ferrule/connector to the next pole. This is a common shock cord attachment for many tent frames.
"HOW TO SHOCKCORD POLES TOGETHER WITHOUT USING ENDTIPS-(IE. RING AND PIN SYSTEM):
For your ring and pin system the best way to shockcord the poles together is to tie the shockcord onto a small washer that is just slightly smaller than the inside diameter of the tent pole. When the washer is pushed up into the pole the insert on the first pole will stop it from going past. You can then feed the shockcord through the rest of the poles making sure to put one pole without an insert in the center or your chain of poles. On the opposite end of the pole sections you again tie another washer onto the shockcord and let it go up inside the pole (note you will not be able to adjust the cord tension after this is done as the knot and washer will be way up inside the pole). This method allows you to shockcord all of the poles together and have a hollow end on each end the pole sections to fit into your ring and pin at the bottom. We have separate insert pieces that will fit up into the poles. This will allow you to glue these extra inserts onto the hollow ends of the poles to give you more structural support in the pin.
DIAGRAM FOR RING AND PIN ASSEMBLY"
From
Quest Outfitters .
butthead