20): The authors first explain that round wheels are better suited for rolling than square ones and therefore better afford (i.e. allow) rolling, but later state that a door handle "affords" (i.e. suggests) pulling, but not pushing. ↑ Gaver, William W. (1991). "Technology affordances". Proceedings of the SIGCHI conference on Human factors in computing systems Reaching through technology - CHI '91. p. 79. doi:10.1145/108844.108856.