Mr. McGrooovy's rivets look like something my kids will use over and over again.  These rivets will let you build amazing stuff using cardboard you can get for free.  

My son is forever building stuff from cardboard.   Every time I turn around he's using rolls of tape to hold his latest creation together.  He's built ramps for cars and marbles, a shield for a medieval play, a car he could climb inside, and endless other creations.

These rivets look like they will be much simpler to use, hold together better, be reusable, and best of all, they can be removed without tearing the creation apart.

The website includes for free plans for a backyard size castle, fire engine and pirate ship made refrigerator boxes.  I'm sure my kids would love to try those, but I think we'll start out with smaller creations to get the hang of it.

We've placed our order and are waiting for it to arrive.  I'll let you know what happens when they get here. They're here.