The function of bon toro is similar to that of "sotoba" (a pagoda-shaped wooden tablet set up by a tomb, on which phrases from a sutra or the like are written for the repose of the dead's soul), and bon toro is set up around the grave by the visitor during the season of Obon.
機能としては卒塔婆に相当するもので、盆の時期に墓参りを行う者がその墓の周囲に立てる。