What are they?[]
Two sockets as they can be seen in their natural habitat.
Auxiliary Power Sockets, or Sockets for short, are used with stationary units to provide buffs (whether that be to the item, your team, the connected outpost, etc.). They, in short, are a power provider. For the majority of turrets, they simply buff the turret's HP or DPS. However, units like the Lunchbox can buff your team or the connected outpost, but will not work when not connected to a socket. A full list of these can be viewed at Socket Powered Units, which includes the Lunchbox, Moneymaker, and a few others. An important more is that socketed units heal for 30 HP per second.
In the vanilla maps, there are 0-4 Sockets per Outpost, and 6-10 sockets per Fort (including the four outer pillars).
Map Editor[]
In the Map Editor, the Auxillary Power Socket can be found under the prop "FortBasePad." If you wish to see socket-related things, search "pad." One more thing to note is that, no matter what, the Socket will always connect to the absolute nearest outpost. Wires cannot change this behavior. This is useful for using things like the combo Wireless Socket.