Question: To ensure two boards are cut to the exact same length,
Options:
measure the first board to the desired length and cut it.  Then use the first board to measure the second board to the exact same length.
measure the first board to the desired length and cut it.  Then use the first board to measure the second board, add an inch, and cut it.
Answer: measure the first board to the desired length and cut it.  Then use the first board to measure the second board to the exact same length.