How do I apply a procedural generated scratch overlay across multiple mesh What is going on


100% procedural texturing is part of the goal
Each board is an individual mesh  
Exact same material is used on each mesh
Material's nodes add a random value to Object Texture Coordinates to the z coordinates to generate the variations in the wood grain





Goal


Procedural scratch across multiple mesh
Image texture is not an option
Using Geometry Node's Position socket you are able to mark surfaces from a global coordinates perspective.  Simply add an overly once you have a desired pattern generating.  Here is an EXAGERATED example just to show what happens.  Kepping in mind all the boards have exactly the identical material applied. Eliminating the need to apply image textures.


Of course the final scratching will be much more refined and detailed. :)