Horizontally extendable ladder

A horizontally extendable ladder comprising:

• at least two ladder frames that includes
• at least three rails having two outer rails and a middle rail set between the two outer rails, and
• a plurality of rungs disposed between the two adjacent rails;
• wherein the rungs are equally spaced and arranged horizontally between the two adjacent rails from top to bottom;
• thereby the ladder frame is formed by the two adjacent rails and the rungs arranged between the two adjacent rails;
• a first pivot shaft is set on each of two ends of the rung and is pivotally connected to the rail so that the rung is able to be rotated synchronously between the two adjacent rails;
• wherein the rung of the ladder frame is able to be rotated and folded between the two adjacent rails by the first pivot shafts on the two ends thereof to form a first collapsed state;
• wherein the two adjacent rails are able to be moved close to each other and held together so as to reduce width and area of the ladder frame when the rung of the ladder frame is in the first collapsed state;
• wherein the rung of the ladder frame is rotated and extended between the two adjacent rails by the first pivot shafts on the two ends thereof to form an extended state when the two adjacent rails in the first collapsed state are extended horizontally;
• wherein the two ladder frames are able to be extended synchronously to form the horizontally extendable ladder in an extended state with extended width and area of the two ladder frame;
• or only one of the ladder frames is opened selectively and fully to form the horizontally extendable ladder in an extended state with width and area of the single ladder frame.