I think he means to relocate the hole in the rail so it lines up with the mislocated hole in the slate. If the hole in the slate is one inch south of where it should be, make a hole in the rail 1 inch south. Most of us are more comfortable working with wood than stone. Properly locating holes is preferable to matching the improper location, especially if the table gets taken apart and reassembled in the future. Figuring out which "identical" parts fit in the "identical" locations is always a test of patience.In slate?