The core culture or Pengngan Chamorro is based on complex social protocol centered upon respect: From sniffing over the hands of the elders (called mangnginge in Chamorro), the passing down of legends, chants, and courtship rituals, to a person asking for permission from spiritual ancestors before entering a jungle or ancient battle grounds. Other practices predating Spanish conquest include galaide' canoe-making, making of the belembaotuyan (a string musical instrument made from a gourd), fashioning of åcho' atupat slings and slingstones, tool manufacture, Måtan Guma' burial rituals, and preparation of herbal medicines by Suruhanu.