An extendible or adjustable length level is provided. The level includes a locking mechanism allowing the user to fix the level at a selected or desired level. The locking system allows the user to lock the level at the desired length and provides more effective and robust locking than conventional expanding levels. In some embodiments the locking mechanism is designed such that translational movement of the user-actuated control (as opposed to rotational motion) is used to move the locking mechanism into the locked position.