Because it was started when illegal dumping was not a problem, this may have originated in an attempt to prevent people from urinating outside by drawing the shape of a torii in red paint at the bottom of a fence.
これは、（以前は不法投棄はほとんど無かったので）立ち小便抑止の為、塀の下方等に鳥居形を赤の塗料で描いたものが原点のようである。