Slacklining is a practice in balance that typically uses nylon or polyesterwebbing tensioned between two anchor points. Many people suggest slacklining is distinct from tightrope walking in that the line is not held rigidly taut (although it is still under some tension); it is instead dynamic, stretching and bouncing like a long and narrow trampoline.
Having tried slacklining once before, can positively say that these guys are insane to even think of trying something like this.
