As I said in Part 2 of this series, if you're joining the active duty Navy or active duty Air Force, your job selection is going to be done at MEPS (by "Job Counselors"), not the recruiting office. For the Guard and Reserves, recruiters work directly with Guard/Reserve bases in the local area, trying to fill specific job vacancies in those units, so they have more to do with the job selection process. Marine Corps recruiters work with recruits to fill job or enlistment program quotas that are given to them from their headquarters.
Army recruiters (including Army Reserves and Army National Guard) have access to a system called called FSR2 or "Future Soldier Remote Reservations System." Any applicant that is a high school senior in good standing or a graduate of high school may pick their job off of the "Request" system as if they were in MEPS from the recruiting station, as long as they "pre-qualify" for enlistment. They then have seven days to go to MEPS, take the physical and then do the final signing for that job. The system also provides shipping date for the job, enlistment bonus/college fund amounts authorized for that job, etc. Of course the job isn't "guaranteed" at this point. The applicant will have to meet the qualifications for the job (ASVAB, physical profile, security clearance requirements, ect.), which will be determined during the MEPS trip (more about this on the next page).
To get the job of your choice requires two things: (1) There must be an available vacancy for the job, and (2) you must be qualified for the job. Availability is "luck of the draw." The services forecast what jobs will have vacancies at specific times during the recruiting year ("vacancies" are determined not only by whether the skill is needed, but also, whether/when there are available training dates for that job). For example, even if the service you're trying to join needs linguists very badly, and you qualify for the job, if all the school dates are already reserved at the Defense Language Institute for the foreseeable future, you're probably not going to be able to get that job. Job Qualification. Job qualification is based on several factors. Most significant are your ASVAB "line scores." The services have assigned minimum ASVAB line scores to each enlisted job. They've learned, though years of experience that these specific score requirements are what an applicant needs in order to successfully make it through the training for that job. ASVAB line score requirements for specific military enlisted jobs can be found in our Enlisted Job Description pages.
In addition to ASVAB line scores, many jobs require the applicant to qualify for a Security Clearance. Therefore, if the applicant has anything in their background that may prevent approval of a clearance, the MEPS job counselors are unlikely to allow the applicant to reserve that job. Some jobs require additional testing. For example, any job that requires one to learn a foreign language, requires a passing score on the Defense Language Aptitude Battery (DLAB).
Different jobs have different physical requirements. When one goes through their medical examination at MEPS, one is assigned a Physical Profile, which is a series of numbers that indicates the member's medical condition in designated medical areas. In order to reserve a job, one must meet the minimum physical profile required for that job.
Some jobs, especially those designated as "direct ground combat" jobs are restricted, by law, to males only. Some jobs (especially in the Army and Air Force), require a minimum lifting ability, which must be demonstrated before the job can be reserved for the recruit.
"Guaranteed" Jobs. A word about "Guaranteed Jobs." It's important that you understand what a "guaranteed job" is in the military. If you have a "guaranteed job" in your enlistment contract, it does not mean you will get that job, come Hell or high water. There may be reasons, after you enlist, that you can't get the job that your enlistment contract "guarantees." What happens in that case, depends on the situation.
In general, if you are denied the job in your contract due to something beyond your control (such as the service phased out the job, or downsized the job, or made a mistake and discovered that you don't qualify for the job, or you are denied a security clearance -- not due to giving false information), then you will be given the choice of applying for a discharge, or choosing a new job from a list of available jobs that you qualify for. In this case, the choice is yours (It should be noted that while these situations have been known to happen, they occur rarely).
On the other hand, if you fail to qualify for the job due to a reason within your control (you fail in training, you get into trouble, or you give false information on your security clearance application and are denied a security clearance), the choice is not yours. The military will decide whether to discharge you (throw you out), or to retain you and retrain you into a job that you qualify for. In this case it's the military's choice.
Each of the services have different policies/procedures when it comes to "guaranteed jobs."
Army. In the Army, an enlisted job is called an "MOS," or "Military Occupation Specialty." The Army is the only service that offers a guaranteed job (MOS) to everyone. The Army has no such thing as an "open" or "undesignated" enlistment. However, the MOS's offered to you, might not be the one(s) you wanted. It depends upon your qualifications and what jobs have current/projected openings. If the job you want is not available, your only choices are to choose a different job, or not enlist. On the negative side, of all of the services, the Army has the worst reputation for working soldiers in jobs that have nothing to do with what their MOS is.