Scrape marks in the post of my fence. It's mainly on the 4x4, but small amount on adjacent 2x4s.
Wasps
Chew marks from paper wasps. If the wood were stained, their nests would be tinted that color.
Definitely wasps. Check around the house for nests.
Do you have a large amount of paper wasps or hornets? This is what most of the wood in my yard looks like because they use it to make their nests.