Ranger Bands -- Holy Rubber Band Batman!

Just cut up an old bicycle inner tube, can't get much simpler than that.

"Ranger Bands", used originally by the Army Rangers to tie down and quiet their hanging straps etc.

Loved by outdoorsmen, these have thousands of uses, can be cut to any thickness, and won't dry out and break anytime soon.

Cut them thin to stretch them out more, and thicker to increase strength.
They are wicked strong.

Great for anything you need to strap down, attach, etc. and make sure it won't come loose.  

PS. They burn very nicely and can be used to start a fire in an emergency

(they are rubber, so stay away from the smoke).