The length of snakes are 61 ± 4 cm; the radius of snake is 1 cm; the width between constraints are respectively 2 cm, 3 cm, 4 cm, 5 cm, 6 cm from top row to bottom row. This research was published in Journal of the Royal Society Interface in the paper: Buckling morphology of an elastic beam between two parallel lateral constraints: implication for crawling snake between walls by Xi Chen and Junfeng Xiao. The doi link for the article is http://rsif.royalsocietypublishing.or.... This video is also the movie S3 in the ESM of reference 6.