Abstract: A passive mountaineering chock or stopper is provided and which comprises of a prismatoid body having a first skewed hexagonal base, a second, parallel hexagonal base, and six lateral trapezoidal faces forming three opposed pairs of faces, each face with one side lying in the first skewed hexagonal base and an opposite side on each trapezoidal face lying in the second skewed hexagonal base, where lengths of the sides of the skewed hexagonal base substantially obey the following relationship: a first side has a length, a fourth side opposite the first side is slightly larger than the first side, a third side, immediately adjacent to the fourth side, is the same length as the second side, a sixth side, opposite the third side and adjacent the first side is slightly longer than the third and fourth sides, a fifth side, immediately adjacent the sixth side is the same length as the sixth side, and a second side, opposite the fifth side and adjacent the first and third sides, is longer than the fifth and sixth side