Helmet Liners

Helmet liners provide comfort and safety, ensuring the skull does not contact the sides of the helmet potentially leading to brain damage.

Modern/Sport/SCA
A spangen type construction of sorbothane or similar modern camping foam eg: "Smurf blubber"

Zwiehammers vendel liner
This can be done by making a shell of close cell foam, two halves darted in the center. These two halves are joined together with barge cement at the joint. This is then covered by suede, cut in the same shape as the padding, glued to the outside of the shell of close cell foam with spray upholstery adhesive. This just fits snugly into the helm, it is not anchored to it at all.

Suspension
Multiple panels quilted and stuffed and tied at the top, sewn in to the helmet via small holes around the edge or sewn to a leather band riveted to the helmet bowl

Jousting
Many late joust specific helms like frogmouths used special systems of straps and padding to suspend the head inside the helmet.