Every so often I like to pose a STEM challenge to one or both of my kids. We've done some really fun challenges like building bridges strong enough to support 100 pennies with just 3 notecards and some tape. I recently ran across a post where they used a clothesline and pulley to construct a Lego zip line. Since the kids' nana had just recently given them a set of Classic Legos , this seemed right up E's alley. And boy, was I right! First we looked for a plastic clothesline pulley at Walmart, but they didn't have any. Then we went to a small local hardware store, but only found expensive metal ones. So we tried a big name hardware store and finally hit the jackpot! Pulley: $2.38 Clothesline: $2.78 You could buy them on Amazon here and here , but they are more expensive there. Next he had to build a platform and figure out how to attach it to the pulley. Then he tested his contraption and discovered it arrived at its destin...