Over the night of May 8–9, the Confederates were busy erecting a series of earthworks, more than long, starting at the Po River, encompassing the Laurel Hill line, crossing the Brock Road, jutting out in a horseshoe shape and then extending south past the courthouse intersection. The earthworks were reinforced with timber and guarded by artillery placed to allow enfilade fire on any attacking force. There was only one potential weakness in Lee's line—the exposed salient known as the "Mule Shoe" extending more than a mile (1.6 km) in front of the main trench line. Although Lee's engineers were aware of this problem, they extended the line to incorporate some minor high ground to Anderson's right, knowing that they would be at a disadvantage if the Union occupied it.