I wish my grandpa was this cool.
Paul Gregg, a former Boeing engineer, decided to make a backyard roller coaster for his grandkids.
Gregg built the coaster as a retirement project after more than 50 years with Boeing.
He believes that it's important for kids to have fun while being safe, and so the coasters are equipped with seat belts.
Naturally, Gregg has more engineering experience than most of us so his DIY post is pretty intricate.
For those ambitious enough to want to make their own backyard coaster, Gregg has written an e-book on the process.
Before any children were placed in them, so you know it's safe!
Or Best Grandpa Ever?