David,

Shy's Hill was, what we call in the military, key terrain on the left flank of the Confederate line. The line was "anchored" here and if the Confederates could be (and they were) dislodged from this location then their avenue of eggress would be threatened.

I hope this helps.

Respectfully,

Gerald D. Hodge, Jr.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment
http://39thgavolinfrgt.homestead.com/39thHomepage.html