A friend just had a new oak floor installled 3 weeks ago. It has been sealed and then finished with 2 coats of poly.
They have been very careful but when moving in a very large and heavy refrigerator they put a few scuffs in the floor. They are pretty good scuffs but not through the finish.
Is there anything that they can do to repair these marks?

I have on occasion screened individual boards taking care not to screen undamaged boards around them and using a chip brush re coated just the damaged boards following the cracks in the boards. The real trick is to match the sheen of the finish on the floor. Gloss is easiest but when you get into semi-gloss or satin it gets a little more difficult to match.

You will have to wait till the finish dries to tell if you were successful or not.

One simple way, that should work is by making a mixture of olive oil and vinegar. One part of each. Shake the mixture energetically, tip a small amount of the mixture on the scratch, and rub lightly into the wood. Leave it to rest for 12-24 hours, and then rub off. Keep on doing this until the scratch lessens, and eventually disappears.