Abstract: A locking mechanism operates to selectively lock and unlock a pair of telescopic tubes. A lock base is fixed to one tube and is formed with an eccentric pin. A lock ring is slidably disposed within the other tube and is slipped over and carried by the eccentric pin. The external configuration of the lock pin and cross section of its associated tube are polygonal or multi-sided to prevent relative rotation. By relatively rotating the tubes in only one direction locking is accomplished and by relatively rotating the tubes in just the opposite direction unlocking is effected. The overall end-to-end length of the tubes can be adjusted by unlocking them, sliding one axially relative to the other and then locking them again.