Trainee Crew Member Steve Porter: 'We use the double sheet bend for attaching lines of different thicknesses together. A prime example is attaching the heaving line to the tow rope. The heaving line is the thinner line, configured to make it easy to throw to the vessel being rescued. They can then pull the line across and grab the heavy tow rope, securing the tow rope to their vessel to be brought to safety.

'The sheet bend can also be done as a single. It can work just as well, but could come loose in certain conditions. We usually do a double as it is more secure and takes only a second longer to tie.'

Step 1: Make a bight (an unenclosed loop) in your tow rope.

Step 2: Pass your heaving line up through the bight and over the far end. Bring the working (tail) end back towards you, under the bight.

Step 3: Pass the working end of your heaving line over the near side of your tow rope bight, under the heaving line and over the far side of the tow rope bight.

Step 4: Repeat step 3.

Step 5: Pull the standing end of the heaving line and the bight tight.