Retractable ladder

A retractable ladder, comprising:

• an inner leg bar, and
• an outer leg bar, wherein:
• the inner leg bar comprises a closed frame,
• the outer leg bar comprises a bottom plate and two straight side plates,
• the two straight side plates are disposed on two ends of the bottom plate,
• the two straight side plates are parallel to and are separated from sides of the closed frame adjacent to the two straight side plates,
• a first portion of the closed frame adjacent to the bottom plate is disposed in a frame having an inner opening defined by the bottom plate and the two straight side plates,
• a second portion of the closed frame away from the bottom plate extends out of the inner opening of the frame having the inner opening,
• a clearance is defined between an outer side of the inner leg bar and an inner side of the outer leg bar,
• at least one lock hook is disposed on an inner side of the bottom plate and is disposed in the clearance,
• at least one curve hook is disposed on an outer side of the closed frame that is parallel to the inner side of the bottom plate and is disposed in the clearance,
• the at least one lock hook is slidably locked to the at least one curve hook to enable the inner leg bar to be configured to slide relative to the outer leg bar along a length direction of the outer leg bar and prevent the inner leg bar from separating from the outer leg bar,
• an inner cross bar is fixed on an inner side of the closed frame, and
• the outer side of the closed frame is parallel to the inner side of the closed frame.