GRUSCHTELING
It means the sound made when you rummage through your Lego bricks looking for just the right piece, according to this page.
Used in a sentence: "When the package arrived, I knew it was the Lego sets I'd ordered, from the lovely gruschteling it made when I shook the box." Or: "When I looked up from working on my latest Lego creation, it was midnight, so I tried not to gruschtel too loudly and wake up Mom and Dad."