From, The Oxford Companion to Ships and the Sea, edited by Peter Kemp, Oxford University Press, 1976.
Rope is wormed, parceled, and served to protect it against the wet, which is liable to rot it.
Worm: The operation of passing a small rope spirally between the lay of a hemp cable.
Parcel: The operation of winding strips of tarred canvas round a rope after it has been wormed.
Serve: The operation of winding spunyarn close round a rope which has been wormed and parceled and using a mallet to obtain maximum tension.
And here is a detailed account if you would like to try it yourself. From, The Young Sea Officer's Sheet Anchor; or, a Key to the Leading of Rigging, and to Practical Seamanship. By Darcy Lever. Charles E. Lauriat Company, Boston, 1938.
Spun-yarn is used for worming, serving, seizing.
WORMING A ROPE,
Is filling up the divisions between the Strands by passing Spun-yarn along them. This is done, in order to strengthen it, for various purposes; and to render its surface smooth for parcelling.
PARCELLING A ROPE,
Is wrapping old Canvas round it, well tarred, which prepares it for serving, and secures it from being injured by rain water lodging between the parts of the Service when worn.
Is clapped on by a wooden Mallet made for the purpose. It is round at the Top, but has a Groove cut in the head of it to receive the Rope, that the turns of the Spun-yarn may be passed with ease and despatch. It is done thus: The Rope is first bowsed hand-taught by a Tackle, then wormed. The End of the Spun-yarn for the Service is laid upon the Rope, and two or three turns passed round the Rope and over it, hauling them very taught. The Mallet is laid with its Groove upon the Rope, a turn of the Spun-yarn is taken round the Rope and the Head of the Mallet, close to the last turn which was laid by hand: Another is passed in the same manner, and a third also on the fore part of the Mallet, leading up round the Handle, which the Rigger holds in his hand. The Service is always passed against the lay of the Rope, so that as the latter stretches, the tension of the former is not much decreased. A boy holds the Ball of Spun-yarn at some distance from the man who is serving, and passes it round, as he turns the Mallet, by which he is not retarded in his operation. The end is put through the three or four last turns of the Service, and hauled taught.
Next time you're on Balclutha, please have a little closer look at the wire rope.