What type of example the hot water bottle is?

The hot water bottle is an example of local dry heat application. The hot water rubber bottle filled with warm water and sealed with a stopper, which is generally used to apply warmth, but it can also serve to apply heat to a specific part of the body. It may also only serve as a container for warmth and comfort like holding a hot cup of coffee between your hands.

Some newer products function like older bottles but use a polymer gel for wax in a heating pad. The pads may be heated in the microwave, which is safer than the alternative. Heating a hot water bottle is not something anyone should do. There have often been problems with premature failure of rubber bottles heating up due to faulty manufacturing, and boiling water is certainly not recommended.