What is the deal with the food tug, does the dog open the tug during the game to access the food?

These tugs are used to entice dogs who have high food drive, but little to no drive to tug. You stuff it with something the dog especially loves and then if the dog puts his mouth on it at all, you mark and reward the dog by opening the Velcro and giving him some of the food from inside. Basically, you teach the dog to tug to get a food reward.

I would probably not ever do this with a dog I wanted to do biting sports or real protection work with but I’ve seen it used with pet dogs and agility dogs with success.