You can make all visleafs be visible from vis leaf where this entity is created. Also you can make a specified leaf visible from all other visleafs. Just place entity in a place where you want overview point. If reversed, place it at the center of a model/entity enclosed in a hollowed area (that are not always visible despite to player's position in the world) you wish to be visible from within the whole map.
Reversed reverse : If set to yes, instead of making this leaf an overview point for all other leafs, make this leaf visible from every place of the map.