Not for nothing are the two ‘locks’ known as the engine room – it is they who provide the power in the scrum. The No 4 is typically shorter and bulkier, and pushes behind the tighthead; you will jump at the front of the line out and must be dynamic to react to a fast throw. In contrast, the No 5 will be a middle-of-the-lineout skyscraper able to win a stream of ball – and the same is required at restarts. Far from just being a big lump, a second-row should be a clever clogs able to read the opposition or deceive them. And vertigo sufferers need not apply because you can be 13 feet off the ground when gathering in those lineout throws!