Some ways to express that (generaly we use words like -grip/hold/cling/grasp etc):
A sloth's grip is so strong that sometimes a sloth stays hanging from a branch even after it has died.
Upon digging into a surface, the force of gravity shifts from the squirrel's paw pads to the underside of its claws. If the surface is porous enough to embed its claws at an angle of 90 degrees or greater, the squirrel can ensure a successful grip and evenly distribute its mass across its claws.
He can cling thight to tree bark while traveling up or down.
...but it isn't just your favorite domestic felines that use their claws to scale the bark: Their much larger cousins, like jaguars, cheetahs, lions, and tigers, also have a penchant for heights.
Curved claws enable the cat to superiorly grasp and hold large prey and climb trees head-first. However, the curvature of claws, size and weight of the animal is great hindrance in climbing down from trees. Therefore, tigers either crawl backwards or jump down from trees, making them the most inferior climbers of the big cat family.