What is it?

[GBNI]

On the Grand Banks the secondary anchor rope exits via a small stainless box beside the windlass.
How does this open to allow rope out?

 

[AnsleyS]

Usually the cover slides up and off letting the line to be accessed from the top. Grab and pull up.

 

[GBNI]

Thanks, the one in question is seized but now I know what it is supposed to do, I can investigate further.

 

[AnsleyS]

Try a heat gun to the top and a little persuasion.

 

[OldDan1943]

Crawl in the chain locker and see if "someone" secured it from the inside.

Take a pole with you and poke at it from inside the chain locker.

 

[PennBruce]

While you're in the chain locker, check that the bitter end of the anchor rode is fastened to the boat.

Bruce