Factory Plates are an alternate method of increasing production. Instead of boosting a single factory with Caretakers or constructors, a factory plate is a cheap way to double a factory's throughput. A factory plate requires a factory of the same type within a short distance (seen as a circle surrounding the factory) to work. When selecting a factory to place, should there be another factory of the same type already placed and friendly, a line will be drawn to it. Moving the factory ghost into the circle will automatically convert it into a plate.
Tips and Strategy
A factory plate is cheaper than a Caretaker, another factory or any 2 constructors, so consider building one as an alternative to a Caretaker for increased production.
Factory plates are very useful in team games, as each player can choose a different factory at the start, and a player can build a plate at someone else's factory should they want that factory's units.
However, for expensive units such as the Grizzly or Jugglenaut, consider a Caretaker instead, as factory plates cannot help the main factory or other plates with creating units. Though should there be a sudden, urgent need for smaller units, a plate will allow the continued production of the expensive unit while the smaller ones are being produced, instead of having to cancel the large unit and switch to the smaller ones.