"Three lines of gear": The concept of prioritizing personal equipment
"Three lines of gear" Who started it or where it started is not very clear. But this concept of prioritizing personal equipment is popular among military personnel, hikers or disaster preparedness. Many countries have adapted this concept to suit their own context and environment.
The Three Lines of Gear is a broad concept that prioritizes your gear, allowing you to add or remove items as needed. For example, if you are on a mission with all your gear, but for some reason you need to slam a door and clear a building, you will obviously have to leave some of your stuff somewhere to be lighter and more mobile. Or, in some situations, you will have to keep or leave some of your gear. The Three Lines of Gear can help provide a rough framework for how to prioritize the items you carry.
First, Second, and Third Line
First line gear should be the basic equipment that is necessary and can be carried at all times ( Everyday Carry ) every time you leave the house. Typically this includes a wallet with small bills, a fully charged cell phone, a concealed carry gun with a spare holster and a folding knife , paracord, a high powered flashlight (at least 800 lumens), etc. All of this equipment can be in a go-bag, a 24-hour backpack or a 72-hour backpack for long distances.In a combat or disaster situation, first line gear may focus on survival items such as fire starters, portable water filtration systems, maps and compasses, fixed blade knives, emergency blankets, emergency food, first aid kits, and signaling devices depending on the situation and needs.
Second line gear This is the primary gear used for the mission, such as your primary weapon and ammunition (around 1 basic load), an IFAK (Immediate Reload ), a radio with extra batteries, and an antenna, or maybe a water bladder on your back. All of this can be customized based on the mission and needs, but it is important to load everything and familiarize yourself with the entire kit, learn where everything is, and make sure you can do things like shoot, run, crawl, and get in and out of vehicles. Also, make sure your chest-rig or plate carrier is compatible with the Third Line equipment packs or backpacks.
Third Line has everything you need for a 72-hour trip or patrol, but that isn't necessarily accessible or mission-critical: emergency food, water, clothing and bedding, a USB-powered solar charger, camping essentials and repair tools.
The key principle of the "Three lines of gear" concept is to organize your gear so that it complements each other, and remember that the more important a piece of gear is to your mission or survival, the closer it should be to your fingertips and be within easy reach.
And finally , let me summarize briefly like this.
First line = Survival
Second line = Fighting
Third Line = Sustainment
Source
First, Second, and Third Line Gear… – Emergency Survival Charts
https://www.offgridweb.com/preparation/layering-your-edc-survival-gear/