We just cut out a 7 foot section out of a 6×8 white oak beam today. The beam was incredibly tight white oak with great patina, but I digress. The section was scarf joint. When the old barn builders needed and extra long span of wood (something more than 20 feet), they would often join two pieces of wood together with angled cuts and sometimes some iron work to create a scarf joint.
There are actually many different variations of scarf joints and it’s fun to look at how different builders worked. This one used metal bands of sorts. These were original hand forged pieces. Some guys will just use bolts and big washers. Others will use a wood peg to tighten the joint.