Step 1: Intro
Step 2: Gathering Materials
1. Bottle of some sort with screw on cover, size matters only for what you are doing with it.
I found that soda bottles work well, and water bottle, such as poland springs just collasp, I suggest a Nelgean, or something similar,
2. Find water.
3. Find heating source
4. Find something to heat water in....
5. Oven mitt
6. Cloth to wrap bottle in
7. String or something similar, that will be able to hang around your neck without causeing you discomfort.
Step 3: Building
second... boil water, rolling bottle works really nice
once water is boiling, pour into the bottle, be careful, the water is hot, use oven mitt to do this.
now... put cap back onto bottle, make sure it is tight, and wrap bottle in cloth, I made a pouch that holds a soda bottle, and hangs around my neck.
Now, if you don't have a cloth sack like me... tie a piece of sting around the neck of the bottle... then hang the loop around your neck... place jacket over it, and go outside, makes even the most bitterly cold day bareable....
if you don't like the idea of hanging it around your neck, put it in a pocket, or something similar.
Step 4: Placement
Now if you are camping out, and have a cold sleeping bag... take a hot water bottle and put it in your bag like 10 minutes before bed... then when you crawl in, it will be all warm... then if you want, before you go to bed, make another hot water bottle, and place it in bed with you, keeping the first one there...
but it is not really needed.
Now, if you are traveling around, and need to keep warm, take a water bottle and hang it like a necklace, one in front, and in back, under your coat. I have done this, and it kept me warm for like 2 hours, but it was also 2 below zero, with a high windchill, my hands were numb, but the center of the body was very warm.
Now if you don't like the idea of a bottle on your back, but want to keep your back warm, take a back pack, and place the bottle on the part that will touch your back. This is also convenient if you have water or something that you want to keep from freezing. I took my bottle, filled it with hot coco, and wrapped what would be the exposed side in a scarf, spare socks, gloves and hat, then put my water bottle right close to that, and through out the day, while other people were struggling with frozen water bottles, I was sipping mine.
As for keeping the rats warm, place the bottle in a sock or something as to keep them from burning themselves, and place in the cage where they can cuddle up with it.
(no picture for this, just use your imagination)