SDCL § 45-4-3: Marking surface boundaries of claim.

Surface boundaries shall be marked by eight substantial posts, hewed or blazed on the side or sides facing the claim and plainly marked with the name of the lode and the corner, end, or side of the claim that they respectively represent and sunk in the ground; one at each corner and one at the center of each side line and one at each end of the lode. If it is impracticable because of rock or precipitous ground to sink such posts, they may be placed in a monument of stone.