Solid Hardwood, Engineered and Laminate Flooring - replacing hardwood boards

I am currently refinishing the hard wood floors in my house. Once I pulled up the carpeting I saw several large holes that were cut in the floor for the old furnace ducts and cold air return grates. Is there a way to replace the boards over those holes? I looked at the flooring and it apears to only be about 1/4 to 5/16 of an inch thick. Any and all info will be appreciated. Thanks in advance.

Yes these repairs can be made. The problem you will have is finding material to use for the repairs. Often times you can use flooring from a closet to make the repairs. the question is do you have enough to do it. 1st you will need to fill in the holes with a good sub flooring material ie ply wood. with out looking at it the thickness will have to be determined. Repairs can be tricky you might want to call a pro to do the repairs and do the refinishing yourself. It takes alot of knowledge to get a repair to blend with the rest of the floor. You can see some examples in the repair section of my web site.
Philly