When the vessel is dropping her anchor, the captain would like to know from the officer at the anchor station, how much chain is being paid out to sea bottom and to determine if there is enough scope available for this purpose.
People have come up with all sorts of systems for marking chain. The most popular two are using jubilee clip/wire or paint of chain links.
Anchor chain which has been officially tested under the Anchor and Chain Cable rules, 1970, is to be marked by two ways :
1- Officially- to indicate S. No. and letters of certifying
authority(on every shackle at each end of cable & 30 meters).
2- Generally -by the crew, staff or dockyard.
All other important details about anchor & chain will be given in the anchor cable certificate issued by the manufacturer and certified by the competent authority.
The purpose of marking anchor cable is to show the number of shackles/amount of cable being paid out to sea.
The marking starts from the anchor shackle towards the chain locker. To indicate the first joining shackle, which will be 27.5 m from the anchor shackle, the first link on each side of the joining shackle is painted white & the third stud is bound with seizing wire and lugless joining shackle will be marked red, and so on for 2nd, 3rd etc. When the cable is running out, even quite rapidly, white marking on the cable may be seen provided the markings are well painted. See image to understand