A manhole cover is a removable plate that forms the lid over the opening of a manhole. Primarily made from materials like cast iron, steel, or composite materials, manhole covers are designed to protect the underground infrastructure and ensure public safety. The LTA/SDRE14/4/GRA8 refers to specific design and performance standards set forth by the Land Transport Authority (LTA) in Singapore, ensuring that manhole covers can withstand heavy loads while preventing unauthorized access.