This is mainly written when a jobseeker is applying for an existing vacancy at a firm of his liking. One need not know the addressee by name but it is always imperative to ask ahead and address the person by their names. It points out the details that may be left out on the resume and also serves to sell you as the right person for the job.
Sample business application letter
Solomon Holmes Security Group,
4th Floor Security House,
46456 Bendor Heights,
6th June 2006.
Ref: Security Guard Vacancy
Following your job advert in the Weekly Mirror of the 21st May 2006 for the above position, I wish to express my interest as an ideal candidate. My experience is lengthy with 9 years of relevancy with the oldest Security group in the locality. I have worked in banks, ranches, city bazaars and also shopping malls in those years. The occurrences of security threats are numerous and it takes greater wit and sheer strength to apprehend suspects. I have managed to successfully capture seven of them single handedly and received numerous awards for them. I anticipate your invite to meet with you to discuss how much further I could be of benefit to your group.