John is indeed correct that there were MANY stone walls that came into play at gettysburg. I use maps by Bachelder and by Warren to consult when I set up a scenario for Gettysburg. A wooden fence is easier to tear down and pass through.
Stone walls take time.
The 2nd day's field was dotted with many stone walls. There were a huge number of them on East Cemetery Hill that Hays and other Rebel brigades had to cross over and negotiate. Stone walls were on Culp's Hill as well near Spangler's Meadow. On LRT, Union soldiers erected stone breastworks to augment their defense.