shin up / down (something)
Definition: to climb up / down something such as a rope or pole quickly and easily using your hands and legs to grip it.
E.g.1: When my parents sent me to bed early, I used to climb out of the window and shin down the drain pipe to play with my friends.
E.g.2: The only way to enter the tree-house is to shin up this rope.
This phrasal verb can’t be separated.