Paul McCartney wrote this after fixing the roof on his farm in Scotland. McCartney said the song was "about the hole in the road where the rain gets in, a good old analogy."
This was the first time The Beatles used a studio other than one owned and operated by their record label EMI. The takes in this new studio - Regent Sound Studio, located in Tottenham Court Road, London - were numbered 1-3. They returned to Abbey Road the next day however, recording " A Day In The Life." (thanks, Matt - Lancaster, PA)
It was rumored that this was about heroin, as in "getting a fix." There is no truth to this rumor.
George Harrison became annoyed at the number of times Paul re-recorded vocals for this song, later saying he did almost nothing during the recording of the album but sit around all day listening to Paul singing the words "Fixing a hole" all day. (thanks, Jonathon - Clermont, FL)