What were Sherman's hairpins?

Answer 1

"Sherman's hairpins," also called "Sherman's (or Jeff Davis) neckties," were made by Union solders from railroad rails, to prevent their reuse by the Confederates, during the burning of Atlanta, GA, after its capture by General William T. Sherman in the American Civil war. They were made by heating the middle of the rails until red hot, over a bonfire of railroad ties. When a rail was sufficiently hot, a team of soldiers would grab it at the ends, and run with it full tilt, into some nearby tree or telegraph pole. This bent the rail in the middle, into a shape resembling a "hairpin" (or "necktie"). Thus badly bent, the rail could not be straightened enough to allow the Confederates to use it again. The name was supplied by the soldiers engaged in the work, as a bit of (Yankee) humor.