A lot of tugs do not use the spring like the one in that photo, although the deep sea tugs I was on did. The usual layout was:
Main tow wire to spring. Spring to pennant. Pennant to bridle (the bridle being on the tow.)
The bridle could be chain or wire. It could be fitted with a 'Monkey's Face' - which is a triangular plate with three holes cut into two upper corners and one lower centre. The fastening for which is self explanatory.
AHTS when towing rigs used to use a wire pennant between the main tow wire and the towed vessels bridle.
I know many of you are not professional mariners but the nomenclature! The chain
never goes through any leads! The chain is arranged in a V fashion off the tow and hooked / connected up to a shackle which is itself hooked up to the pennant. The shackle has a heavy pin and a fastener in the end where it comes out of the bow, which is hammeredv flat to stop it working free- it's like the big boy version of the old 'seizing' of a shackle pin to stop it falling off. In the photo, the chain is passing through the stern hydraulic pins and - from what I can make out - has one turn in to 'lock it'. You couldnn't work with it free as the weight would carry it over the stern! When the tow is all fast, the pins disappear down into recesses leaving the stern uncluttered to allow for play. It also looks like they have one end of a bridle aboard, and the man nearest the camera is leading a light line aft, so maybe they are about to pass it over and heave the other leg inboard to then shackle to the pennant (small wire bent almost 's' shape on he after deck near to the pins themselves. Once they have connected both up, they would 'stream' the tow out - possibly on a short 'nip' when leaving harbour, lengthening it when they reach the open sea.
BTW, those big springs were made (back in the old days when I was a roughie toughie tugman!) of Egyptian cotton. Good elasticity but trust me, they were bu**ers to handle when wet! Also, on trips through the Suez, one eye was always kept on the spare spring as the Egyptians would try and de-strand as much of the spring as they could if you didn't keep your eyes on them! Maybe they felt nostalgic and wanted to bring some home......?
It was never referred to as a 'junk' spring! It was simply a 'spring'!
Jonty