Transcendental Doorknob

Wondrous item, rare You can use an action to put this portable doorknob on a surface like a wall or a ceiling, and pronounce its command word, which is engraved on the doorknob's back. The doorknob immediately transmutes both sides of the surface into a 5 ft. wide and 7 ft. high wooden door with golden hinges, unless the surface you put the doorknob on is smaller than this dimensions, or if both sides are more than 5 ft. appart, in which case the door cannot be opened. The door doesn't have a knob on its other side but can be opened if you speak the command word of the doorknob. A creature that doesn't know the command word cannot open the door from any side and cannot remove the doorknob from the surface. When removed from it, the door disappears as the surface reverts back to its original aspect. If you possess the key of a particular door of approximatively similar proportions you can insert it into the keyhole and create a portal between the two doors as long as they are within 1 mile of each other for as long as the doorknob is not removed. In this case you can open the door created by the doorknob even if it is created on a surface thicker than 5 ft.