Minecraft wiki entry for Village_chaining, associated text: The village border extender is a valid house that, as the name suggests, extends the border of a village so that the center is closer to the center of another village. The extender should always be placed as close as possible to the other village, but must still be closer to the village that needs extension. After that, the further door(s) to the other village's center is removed, so that the extender becomes the center of the village, allowing it to use another extender to continue the process until it cannot get any closer with this method. After the extended village has reached that spot, more doors can be added to it & the other village so they both have enough doors to spawn iron golems.