Tools you will need to get the hardwood repair done: Circular Saw, Hammer, Cat’s Paw/Trim Pry Bar, Wood Chisel, Multi-Tool, Brad Nailer:

Pet stains or worn out boards will need to be replaces when they are beyond saving. First find the boards you will complete replace it.

• Mark the Boards – I mark the specific boards I will be removing very clearly along their entire length so there are no mistakes. 
• Determine Thickness – You need to find out how thick they are (this is important!). You need to know how thick the boards are so you can set the depth of the cut on you circular saw properly. Most old wood floors are between 1/2″ and 1″. The best place to find the depth is to remove a floor heat register or pull up a threshold. The threshold is less fun. 
• Set Saw Depth – Once you know the thickness of your flooring, set your circular saw to just a hair deeper than the thickness of the flooring (about 1/32″). 
• Cut 2 Lines – Make 2 parallel plunge cuts into the floor board along its length with the circular saw. Start and finish as close as you can to the ends without crossing into the next board. You’ll essentially be cutting the board into three slimmer boards. One piece will have the tongue, one piece the groove, and the middle piece will be free floating. 
• Finish Cut With Multi-Tool – To finish the cut you need a multi-tool or chisel. Cut the small amount of wood remaining to the end of the board so that all three pieces of the board are completely independent of each other. 
• Remove the Pieces – The middle piece should come out easily with a pry bar or even your fingers. The groove side will likely need a bit more coaxing with your pry bar. The tongue side will have been nailed down and so you’ll need to use the cat’s paw the either dig out the nails or simply tear the remaining piece out. This side usually breaks a few times on it’s way out. 
• Clean Up – Vacuum out all the saw dust and make sure the tongue and groove of the remaining boards are clear of any remaining wood and in good shape.