Old Wood is a the upgraded version of a Wood Frame and can also be upgraded further into Reinforced Wood. It can not be crafted using other materials, the only ways to obtain Old Wood are through upgrading a Wood Frame or using the Creative Menu.
Old Wood can be created by simply clicking on Wood Frame with wood plank in hand.
It is possible to upgrade Old Wood into Reinforced Wood. For upgrade you will need 1 Wood Plank.