I was recently on vacation in California. I was in a shop in Sonoma and saw this. If you look in the first picture, you can see both sled runners. Someone had take the runners and made a shelving unit out of them. The second picture shows the bottom of the sled and this was the interesting part. The runners had a ton of slots cut in the wood and in each slot was a knapped piece of flint. When I asked what it was originally used for, I was told they were the runners on an old sled that was pulled over wheat stalks to separate the wheat grain from the stalks. I thought it was pretty cool the way the knapped stones was used.