memories. I haven't heard mention of D logs in a long time(they aren't exactly new). The first job I ever had in the construction trades was to help build a couple vacation homes up in northern MN in 1966. They were built from kits of pre-cut logs made by a company in Boyne Falls MI. About 6"dia, they were curved for a log look on the outside, milled flat the other 3 sides. They were stacked and held together with 10" spikes and a caulked spline that fit grooves top and bottom and resulted in a finished interior face with a chamfered wood slat appearance. I made $1.60/ hr.