A survival cache is a container filled with food/water and supplies that is placed in a safe location protected from both accidental exposure and those aggressively searching for your preps (supplies).
A cache is used as a back up to your other supplies.
They are packed with items you believe you will need in a survival situation.
They can be made out of anything, but most people use PVC pipe.
Placing caches in you home or on your property
Caches can be placed in the ground or hidden in walls, furniture, or just about anywhere you can imagine. Just make sure you take into account your local hazards, like flooding, so that you pick an area that gives the cache a good chance of survival during an event.
Placing caches along a route
I cannot say where you can or cannot legally place a cache; you will have to make that decision.
You should place them at logical distances from each other, depending on how you plan to travel.
You should also place caches along different bug-out-routes so that you have multiple escape routes.
Remember where you place them
If you cannot remember where your cache is, you will not be able to benefit from it, so make good directions and include them in your disaster plan.
When making your directions, remember to take into account the possibility that landmarks may get destroyed during a disaster. Knowing how to use a compass and map is a must for every prepper.