They're called Karm forks, made by Karmfork of Norway. Basically, they are two pins that rise hydraulically from the deck. They are not gog type stuff though - they are used to hold wire or chain in place.
The ones you are thinking of are also hydraulic but are called 'Stop' pins and can be raised or lowered and also rotated so they form a sort of fairlead (either closed or open). With it in place, you have a gog that can be moved by hydraulic action whichever way required and without a couple of men on deck to tend to it.
When used in tugs of lesser horsepower in sea and harbour work, they do away with the need for a gog rope. Made by people like Karmfork or Triplex, they are also known as 'shark's jaws' and can take a few variations! They are like forks, with a V out of them for gripping wire or chain. They are often used together so that a gripping device (the Sharks Jaw ) and also used in conjunction with the stop pin.
In my day out in the wild Northsea (when men were men!), we used a wire pennant which was fastened to a Smit Bracket just under the crash barriers. You had to allow the main towing winch to hold the weight on, shackle the pennant to the wire or chain and then ease back on the winch so the weight was transferred to the pennant from the Smit Bracket. With anchors weighing 25 tonnes, and in a force 6 + gale, the word 'hairy' still comes to mind..........!
Jonty