What is a slumber guard? is it like a football mouth piece?

Not exactly...: The slumber guard is a thermoplastic mandibular advancement device that the snorer heats and then molds to provide a custom fit, in order to hold the snorer's lower jaw in a forward extended position. This moves the base of the tongue away from the back of the airway and the soft palate, removing the obstruction and restoring snore-free breathing.