A narrow beam to be ridden over lengthwise, as a test of a rider's skill. A skinny can be of various widths (almost as narrow as a bike tire, and up to 20 cm wide) and various lengths (from one to several meters). Some may also "neck-down" to successively thinner widths, and may also have steps, and be on an incline (up or down). They may be close to the ground, or in some cases dangerously high, and even span small creeks or other obstacles.