designer's own words:the doorknob is made of metal. the shape gradually changes from cylinder to ellipse. it is divided into two parts, and the end part is rotatable. turn it upward at an angle of 90 degrees till the ellipse stands on end and the door is locked. turn it to the start position, and the door is unlocked. according to the change of the knob shape, the user can learn whether the door is locked. so the dorrknob can also be used by the blind.