The theatre map includes a default set of ports on either side.
Sometimes, you may want to remove some or all of these ports from play. Fewer ports makes for a less complex game generally.
Any currently selected port that is not a home port or advanced port can be removed from play.
To remove a port, just untick the 'Is in Play?' tickbox at the top of the screen:
Removing ports can have a noticeable effect on starting odds, not only because a player is losing possible RPs and infrastructure, but also because he is losing the potential trade value between that port and his other ports.
Click here to return to the help page detailing what other port parameters you can change.