Port inventory
From Official Wiki of the Renaissance Kingdoms
The inventory of the port is accessible only by the harbourmaster in the office ((a tab only visible to the harbourmaster in the port).
To deposit objects and pounds inside the inventory (which are necessary for the port construction and for [ship]] construction in the drydocks), the has to obtain a grant from the sheriff or from the mayor. He will be able to move everything from the grant inside the port inventory, pressing the button TRANSFER.
The items transferred inside the port CANNOT be taken out from the inventory anymore. So, be careful what you transfer there.