Each public housing block is considered a vertical community, with a common area built into the design to promote social interaction. Void decks, a term unique to Singapore, refers to the first level which are often left devoid of housing units, hence the word "void". These open, sheltered spaces are intentionally left empty to provide convenient spaces for communal activities such as weddings, funerals, parties, bazaars and polling stations during general elections. Older blocks would feature a single stand-alone shop, often referred to as "Mamashops" to provide convenient doorstep service. Other common permanent facilities built-in void decks may include Residential Committee facilities and offices, kindergartens, medical centres, Neighbourhood police centres (NPC), fire posts and so on.