Your instructor is a tough grader, be sure to dot your 'i's and cross your 't's on your research.
When writing, many people
complete a word before returning to dot the 'i's and cross the 't's. Someone
in a rush might neglect to complete the task. The phrase has been extended
to any job, not just writing.
Crossing the T has also become a naval term. A naval engagement fought
in the Surigao Straight during the Battle of Leyte Gulf, which is in the
Philippines, illustrates crossing the T. That battle (Leyte Gulf) marked
the end of the Japanese navy.
It was also the strangest naval battle in the war. Both sides were totally
confused as to the disposition of enemy forces and both commanders made
mistakes that seriously jeopardized their objectives. Admirals Kincaid
and Halsey had the advantage of numbers and luck and won out.
Warships of the era had guns mounted in turrets distributed over the
ship. Their ability to fire in the direction the ship is pointed
is limited to the front most turrets, rendering the remaining guns useless
for firing forward. However when firing perpendicular to the
ship, all turrets can be rotated and used.
The Japanese ships were caught in a single file line. The
United States ships were positioned at the head of the line in a T fashion.
This formation is known as crossing the T in military circles.
Having crossed the T, the U.S. ships could point all the ship's guns towards
the Japanese ships making it easy to fire on them. The Japanese ships
had the considerable disadvantage of having to fire straight ahead.