"Double two-thirds" is only the most basic requirement for some cities to install elevators in old buildings, that is, the minimum requirement is that two-thirds of the building area and two-thirds of the owners of old buildings sign and agree before they can apply to the Planning Bureau for installing elevators. This minimum condition is only one of the declaration conditions, and does not mean that all the conditions for installing elevators are met. More than one elevator must be installed, that is, 100% will not affect urban planning, 100% will not affect safety standards, 100% will not be opposed by the infringed owner, and so on.