Metal Aglet Barb End Silver 4.5*23mm (10 pk)

Metal aglet barbs are used to secure the ends of elastic or regular cords.

Run the cord along the length of the aglet so that the end of the cord is at the crimp end.
Crimp the aglet around the end of the cord.
Now you can push the crimped end through a hole. Push the entire aglet through the hole. When it is pulled back, the aglet will make a tee and won't come back thru the hole. 
When you want to release the cord from the hole, straighten the aglet along the length of the cord and slip it back through the hole.