... On-Body carry is where your weapon is attached to your body. Everything else is Off-Body. And the key word is “attached.”
As a uniformed deputy I wore a garrison belt threaded through the belt loops of my uniform trousers. I put a Sam Brown gun belt over that and attached the gun belt to my garrison belt by means of short leather straps that went around both belts and snapped in place. These “keepers” anchored my gun belt to me at five points. Put the weapon onto a security holster, attach it to a crane and you could hoist me into the air. My sidearm was attached to my body. It was Zen; we were as one.
And everything else is Off-Body. Example: In the mid 1970s LAPD experimented with gun belts that had no chrome snaps on them. It gave the uniformed officer a very clean and businesslike look, and limited the amount of light that he would reflect at night. But the cons up in prison immediately started practicing for when they hit the streets back in LA. If they were confronted by an officer and could get a hold of the tongue of his gun belt they could rip that gun belt right off of him because all that held it to his body was Velcro. Not only would they gain possession of his weapon but they would also spin him like a top in doing so and disorient him. LAPD went back to wearing keepers and anchoring their gun belts to their officers.
Any holster that can come loose from the body, or any device to hold the gun like a purse or day planner is an Off-Body carry. Fanny packs? Off-Body. Unless you attach it to yourself by a secondary method, it’s an off-body carry that can be removed from you as quickly as a suspect spinning a LAPD officer back in 1975. There is a big quick-connect buckle on that fanny pack and the crooks know exactly what it is and what your fanny pack holds. The same rule goes for paddle holsters. If there is not a way to secure it to your body, it is an off-body carry and subject to being taken from you in a fight.
What has 30-years in law enforcement led me to conclude about concealed carry? Attach your weapon to your body, using a holster and belt. I prefer leather products and carry behind my dominate side hip. The belt threads through your belt loops, though the holster and back through the belt loops. And it should be a good sturdy belt, preferably made by the same company that made your holster so that they properly fit one another.
Over the past decade various “plastic holsters” have come onto the market. For the most part they do not seem to be standing up to the daily wear and tear life of law enforcement officers, but a few of them have. Some of the better ones even have extra security features and the added advantage of a “paddle” device, which secures the holster to the pants securely enough that you may have to undress to remove the holster. But remember that the cons practice breaking the cheap plastic holsters right off of your belt, so we are back to 1975 again.
There is another new option for those who want to be able to remove their holsters without removing their belt. The holster is still a traditional belt slide style, but instead of loops it has flaps at either side that snap over your belt to hold it in place, but it is still easily removed.
There is also the option of using a shoulder holster, and there are many fine shoulder rigs out there that are essentially a “system.” Not only do they carry your weapon but they also have offside pouches for ammunition and handcuffs. If you’ve ever struggled to get a shoulder holster on, you know that they don’t come off that easy, so they are On-Body carry. Downside, after just a couple hours mine starts to get uncomfortable. The upside, I can wear one under a shirt and tuck the shirt in, and leave one or two buttons undone so that I can reach inside to my weapon quickly.
... I have previously discussed ankle holsters. I used them for years to carry a back-up weapon, but my primary weapon was still on my hip. As I said before, sometimes your ankle is too far away and requires you to take your eyes off of the action to retrieve your weapon. I just don’t like carrying my primary self-defense weapon in an ankle rig.The author also has a more general introduction to concealed carry, and the selection of a weapon (see also here).