I believe this is just a mixup in terms. I tried for both nations to generate WS and $ by sending ships with the transport property to every box around. It will only shuffle supply or provide supply for an attached fleet. In that it can help provide WS and $ because fleets stay supplied for a more turns and thus can stay in the appropriate boxes for more turns.
The costs of said ships is so high, however, that most people say it makes no sense building them from an economical point of view. They can be an investment thow to keep the commerce output at a higher level in the later game, even if they don't fully pay off.
Here is what the manual has to say.
Transport ships are here those ships that actually are flagged as transport.
The USA also has the option to transport Supply by sea to coastal areas and ports.
The transport capacity depends on the number of transport ships allocated to the
“World Shipping” box and is displayed on the Transport Assets Panel at the top of
They help indirectly in commerce. Or in blockading.
Ships with low supply will lose cohesion
quickly and must be returned to port to regain it. By manually rotating fully-
Supplied transports to the naval boxes you can maintain them at sea for a much
longer time (until they need to replenish Ammunition in port). This works for
both Blockaders and Blockade Runners.
Blockade runners are mentioned here. It is not obvious that these are the brigs that the CSN can build. Commerce raiders are brigs and frigates. (I confess I don't know, if steam frigates can raid). Merchantmen here mean ships with the actual merchantmen property. With the distinction of so many ships with actual transport capacity, it is easy to mix them up.
I will gladly bow to a correction, but this is best of my knowledge.
The Confederates can try to slip out of their ports with “blockade runners” loaded
with trade goods (mostly cotton historically, but abstracted in game, so you don’t
have to actually load anything) in order to bring in much needed imported goods
for the South. Each active blockade runner will provide up to one Money and one
War Supply per turn to the CSA until it is sunk. The chances of sinking blockade
runners depends on the number, speed and combat value of the USA ships assigned
to Blue Water Blockade in the corresponding box. Blockade runners are generally
viewed by players as a good investment.
Procedure: Move your blockade runner to the Atlantic or Gulf of Mexico
blockade box. Using the “Evade Combat” Special Order is highly recommended.
If the blockade runner manages to sail past USA patrols and reach the blockade
box, it becomes active until sunk or you decide to return it to port (for repairs,
Finally, the CSA can try to disrupt Northern trade by sending out commerce
raiders to sink US merchantmen. Each active commerce raider will disrupt USA
War Supply production. The US can assign warships to the Union Shipping box as
escorts to decrease the effectiveness of CSA raiders and maybe sink them.