Tarring
Most of the ropes on board a ship, i.e. the rigging, especially the standing rigging, were made of hemp and these had to be tarred to protect them from the weather.
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This was done using root or pine tar mixed with linen oil, which was then applied with a brush or rag. To do this, a sailor sat on the bosun's chair and was lowered down the rope, held by his comrades. The Sailor then applies the tar mixture from a bucket as he descends.
The shrouds can be tarred from the ratlines, sometimes combined with fitting new ratlines or re-seizing the existing ones. Lee rigging is typically worked on underway, as drips or spilt tar usually fall into the sea rather than on deck.
This process is repeated every 6 months or so, or more often as needed.