For his 11th birthday, my son wanted his own backyard American Ninja Warrior Birthday Party competition! So we set about constructing a course in our backyard that matches the American Ninja Warrior theme and challenges, at a level that kids can actually do. Here's how we did it:
Here are some quintuple steps I made for the kids in the backyard since they love American Ninja Warrior. These are made with pallets, flat scrap wood for the tops (you could use plywood and even have Home Depot or Lowes cut them to size), and 2'x4's / 2'x6's for the legs (I used scrap wood, so some legs are 4 and others are 6). Let me know if you have any questions.