Abstract: A locking device for a prism pole having a first telescoping member slidably located within a second telescoping member to selectively lock and unlock the first telescoping member relative to the second telescoping member. The locking device includes a housing having a sidewall with a bore extending therethrough. The upper end of the outer telescoping member is attached to the housing and the inner telescoping member is slidably located within the bore of the housing. First and second locking mechanisms, each comprising an annular ring, are disposed within the housing. Each ring includes a bore through which the inner telescoping member extends. The first locking mechanism is selectively pivotal between a first position, wherein the annular ring engages the inner telescoping member to prevent sliding movement in a first direction while allowing sliding movement in a second and opposite direction, and a second position wherein the first locking mechanism allows sliding movement in either direction.