Our dog Dodger will rip apart normal dog toys in about 15 minutes. "Indestructable toys" take a little longer ;)
I learned how to make a monkey fist knot at a juggling festival a few years ago -- just for fun I made Dodger a toy out of rope that managed to keep him busy for at least a few days...
Step 1: Materials
Rope: At least 10.5 feet of 3/8" diamond braid rope -- about 4.5' for the monkey fist knot and 3 feet (X2) for the braid on each end. It's better to start with a much longer piece of rope, tie/position the monkey fist knot, and then trim off the long side. Also, forming the monkey first takes more rope (~6'), which is then tightened down to 4.5'.
Scissors or a sharp knife to cut the rope (Be carefull!)
Lighter to melt the rope ends, to prevent fraying.