Slacklining is a recent sport practise similar to tightrope walking. The strap used in that activity is called “slack”. It is stretched between two bases (tree, posts, etc.…). So, it is practised outdoors, in a natural area, above a river or a sheer drop. The elastic and dynamic material of the slackline makes the walker move in balance. You can also make figures, sometimes using bouncing, as if you were on a long and narrow trampoline.