Colorado Revised Statutes Title 34. Mineral Resources § 34-43-107. Marking boundaries

Such surface boundaries shall be marked by six substantial posts hewed or marked on the sides which are in toward the claim, and sunk in the ground, one at each corner and one at the center of each side line. Where it is practically impossible on account of bedrock to sink such posts, they may be placed in a pile of stones, and where in marking the surface boundaries of a claim any one or more of such posts fall by right upon precipitous ground where the proper placing of it is impractical or dangerous to life or limb, it shall be legal and valid to place any such post at the nearest practicable point, suitably marked, to designate the proper place.