Wood – Add more Polyurethane to recently refinished hardwood flooring

Yes! Cleats are pretty much the standard in hardwood flooring. Typically, hardwood floors have 'tongue & groove' joints that interlock. First, some definitions of terms that I've used in my answer:

Tongue: the part that sticks out of the hardwood piece is called the 'tongue'.

Groove: the slot it fits into is the 'groove'.

Face: the part of the piece that will eventually be the floor is called the 'face'.

Floor joists: these are horizontal panels that run from one end of the room to the other and rest on beams under them. These provide support and you'll install the flooring on the joists, perpendicular to the direction in which they run.

CLEATS

With cleats, you drive the nail through the tongue onto the floor joists at a 45 degree angle. The cleats (which need to be set in) get hidden by the next piece that overlaps the previous one. The advantage is that all except the last piece in the room will have no nail markings on the surface.

The only con is that you'll need a specialized hardwood floor nailer, that can be pretty expensive to buy ($400-500 for a pneumatic one and $200-300 for a manual one). Needless to say, the pneumatic one is less work (but then again, you'll need to get a compressor for it) than the manual (you'll need a 5lbs mallet to drive a 1.5"-2" cleat in fully). However, these tools are easily available for hire at your local HomeDepot/Lowes (assuming you're in the US).

STAPLES

Now, I've never heard of anyone using staples for hardwood floors. It's more a carpet layer's tool. With staples, you'll also have to nail in through the face, thereby leaving marks all over the floor and ruining the appearance. You can probably use staples to lay down the backer board under the hardwood floor (if you're in a cold weather/windy area, this will help insulate the house by preventing airflow through the slots in the floorboard). Using them on hardwood floors is a terrible idea, and wouldn't recommend it under any circumstances.

Just use some of that colored wood putty to fill the holes and put a dot of clear shellac on the putty holes after 3 days of drying. You'll want some powdered whiting to dry out the putty enough to handle (make a wad that doesn't stick to your hands) Once you push the putty into the hole strike it off flush with a putty knife and wipe the excess off with a clean rag. Apply the shellac to the putty only. Do not sand anything. Shellac is handy for many projects. The whiting can be used to make putty from paints and stains, dry out putties for glazing windows & filling nail holes and to thicken paints.