I just hate getting into a sleeping bag that has been sitting at -10 Deg F for the whole day. It is nice to use a Hand Warmer or the MRE Chemical Heater - if you have them. Rocks seemed like something I should try.

I made the normal RING OF ROCKS for the campfire. Several softball sized were placed to ring the fire. Larger rocks on the outside contained the heat.

When the time came, I wrapped the SOFTBALLS in paper towels. I don't like dirt and soot. These I stuffed into small oven bags - turkey bags. Both have an upper temperature limit of ~400F. I stuffed them into the sleeping bag and rolled it up.

That works!

The next test is to use the rocks thru the night for someone who can't stay warm.