Disclosed are adjustment mechanisms and structures including one or more adjustment mechanisms. An adjustment mechanism comprising a casing, first and second arms, a second arm, a button, and an elastic member. The first and second arms are movably disposed in a channel of the casing. The button is operably coupled with the first and second arms and selectively pushes a first end of the first arm out of a first side of the casing and a second end of a second arm out of a second side of the casing. The elastic member abuts the casing and button such that the button is held at a desired position and consequently the first and second arms are held at a desired state under normal conditions. The adjustment mechanisms of the present disclosure provide an easy, convenient and safe means for height or length adjustment.