The scarf joint is an overlapping joint that can be used to connect together two shorter pieces of lumber to make a longer one.
In this case, I was trying to repair the frame of an antique doll carriage so badly damaged that a section had to be removed.
The same technique is often used when joining two pieces of architectural trim such as crown molding in the middle of a long run.
The term probably comes from one meaning of the word "scarf": to make a long tapering cut. Whalers made an incision along the length of a whale's body called a scarf.