Frigates are a vital part of any balanced sea-going fleet. They are cruisers that can operate independently and are swift enough to hunt down enemy merchantmen. The chance for prize money makes them popular postings among officers and men alike!
One way of creating a large, powerful frigate is to take a two-deck ship of the line and, in effect, saw off the top deck creating a single-deck frigate. The first result is that a 64-gun ship can now only carry 44 guns, but the ones that remain are the heavier than those normally found on a frigate, typically 32- or 24-pounders rather than the expected 18s! The second result is that the razee retains the strong timbers of the original 64, making it a robust ship in combat. Thirdly, having lost its upper works, the new ship generally handles rather well under sail. All this work takes time and valuable dock space, of course.
Historically, one of the most successful razees was HMS Indefatigable, commanded by Edward Pellew. In the company of another frigate, Pellew took on - and defeated - the Droits de l'Homme, a French 74, in 1797. During the next year or so, Pellew and the Indefatigable went on to take a further nine vessels.