If you read any guides to getting a job, they always, always tell you write a custom cover letter for every job you apply. When you are applying for 4 jobs, that sounds easy. But if you have a modern job search where you're going to apply to 20, 30 or even more jobs, well, that's a problem:
With Job Hound every single cover letter you write is always available to you. Copy, paste, re-use as needed. And, even better, since cover letters are associated with the jobs and jobs track status like "I Got an Interview", you can easily find just the cover letters that were successful. Additionally the Cover Letter editor lets you paste in the job description when you start writing so you can make sure your cover letter aligns with the job description without having to flip back and forth to a web browser.