A friend has a wooden post in her front yard with a light attached.
There are 2 spots the size of golf balls that, I guess, rotted out and
were filled with what looks like wood putty. She would like them
repaired. At first I thought of using Bondo, but then I figured the
"plug" would just fall out like the wood putty did. At this point, I'm
thinking that the way to go is to turn the hole into a mortise and fill
it with another piece of wood, dutchman style.

Does anyone have any better ideas?

Thanks,

-Phil Crow