Nobori (幟), literally meaning 'banner', had a more specific meaning on the battlefields of feudal Japan. It referred to a particular type of banner denoting units within an army; nobori became much more common in the Sengoku period, coming into use alongside the earlier hata-jirushi. They were long, narrow flags, attached to a pole with a cross-rod to hold the fabric straight out and prevent it from furling around the rod; this way, the flag would always remain visible and identifiable.
Though usually used to represent different divisions within an army, nobori were sometimes made identical, so as to produce an impressive and intimidating display of warrior flags.
Today nobori are used during festivals and sports events (in sports they take the place of the banners and signs common among Western audiences), announcement, appealing something and even identify political party during election campaign.