In response to "A double-tree question" (Farm Collector Letters, January 2008, page 5): This is obviously a double-tree set up for a team of horses to pull something, but it appears to be for a quick release. Therefore it could have been connected to anything that needed to be moved and quickly released.
It might have been used to skid logs out of the woods. A chain could have been attached to the ends with a hooking apparatus to attach to the logs.
I have an old log sled. In my research I read about a problem with the sleds freezing to the ground. A team could pull the sled but could not free it initially. So a second team was needed for just a short time to get the sled free. When the sled was free, they would be released quickly. I am sure you have readers who know a lot more about this.
I enjoy your magazine.
Big Rapids, Mich.