Missed spot of polyurethane

Q: When putting urethane on a floor what can I do if I somehow missed an area in the middle of a floor, and only notice it after I have finished? How do I fix the problem without doing the whole floor over?

This was a polyurethane oil base gloss finish used.

Also, why is it necessary to go with the grain when doing poly if the poly is going to self level?

A: You might try taping off the area with painters tape. Tape the entire boards missed, along the edges and ends. Apply the finish to the missed boards and remove the tape immediately. It is good practice to apply with the grain. If the finish dries faster than normal and you have applied across the grain, you could see fine pin stripe lines left from the fibres of the applicator.

Similar Q: We just sanded and sealed our red oak floors. The hallway is 4ft x 24ft long. When applying the final coat of oil based poly, I noticed I missed one board.. a piece the width of one board and 6 inches long. Can I patch it up without it being noticeable?

A: Probably not but it is still worth a try. I would tape off the affected boards, along the edges and apply a thin coat to what was missed and immediately remove the tape. If the blend is good you are finished. If not, re-coat the entire hallway.