Yukon, those are called grabs. I guess they used to be common, but are now used mainly by a few animal loggers. I have a set that I use occasionaly with my log cart and mules. When I have a log that is higher than the hitch point on my cart, they can be driven in parallel with the log and the part with the hole facing forward has a chain attached. One grab on each side of the log and the chain from each side going straight up to the hitch point on the cart will give the log lift when you move ahead. The "porch swing effect". I only use them on larger logs. They can also be driven in singly on multiple smaller logs or used to hook logs end to end, train style. A several lb. hammer called a skipper which looks like a maul with a pointed end instead of a splitting end, is used to drive them in and out. Dont think you can by them anymore. Mine were made by the Dixie Co.
John