Here's a tricky part that's called the "bowling alley". If this job doesn't get started right and carefully measured along the way, you will get one crooked alley!
This is an example of "tying in" or "feathering in" new hardwoods with an existing floor (the original floor ended where the black tar paper ends). I decided to tie in right in the center of the "bowling alley". Most people would not take this path. There are two reasons for this decision. First, the extra scrutiny on being dead on straight will pay dividends in the "body" of the main floor. Secondly, if done right, you will never be able to tell there was ever anything other than hardwoods there (and it really looks great).
Another tricky spot is around the fireplace. Curves and lines that could throw the most seasoned carpenter off his game.
Look at this -- just beautiful!