ent_hover_turret_tether

This entity is not in the FGD by default.
It should not be put directly in a map because it can only be configured through code.

ent_hover_turret_tether is a point entity available in Portal 2. It is the proper entity to be used to suspend an npc_hover_turret from the ceiling. One is automatically generated between the hover turret and the entity specified in its attachTarget keyvalue, so it does not need to be placed in a map directly.