Success in home canning depends a good deal on how well the canner understands the ‘why’ of each step in the method.
-- United States Department of Agriculture. (1921). Home canning of fruits and vegetables. Farmers' Bulletin, 1211. Retrieved from https://archive.org/details/CAT87202920
Before jars and cans can be processed they have to be filled through either the raw (cold) pack or hot pack method.