There is nothing really special about this. It’s deadwood on an oak tree. The other day I mentioned that limbs should be pruned off at the branch bark collar with a 3-point cut. So that the hormones will be released and the C.O.D.I.T. process will begin. It’s really evident where that line is on this tree. It’s that line where the normal bark stops and forms a 45 degree angle.
Also, if you’re going to cut an oak at all do it when it is dormant if oak wilt is active in your area.