Scratches, dark stains, and damaged boards
Shallow marks and deep discoloration need different treatments. Some stains remain after sanding and may require replacing affected boards. A contractor should explain the likely limits of a repair before promising an invisible result.
Matching old and new wood
Board width, thickness, species, grade, and installation direction all influence a patch. Matching stain does not make every board identical. Ask to see a proposed sample and discuss how far refinishing needs to extend to create a practical transition.
Check moisture and movement first
Cupping, buckling, soft spots, and recurring gaps deserve an assessment before cosmetic work. Tell the contractor about leaks or prior water exposure. Resolve ongoing moisture or structural issues before covering the symptoms with a new finish.