My climbing is a custom movement mode, you turn it on, and then pass in the offsets you want, its used for more than just climbing, the general concept is just to get the hands difference from where you want it to be on the gripped object and then move the pawn to place the hand back there again. So if you were to custom code it for a base pawn, its just storing initial grip location on the object, and moving the pawn by the inverse of the CurrentPosition - InitialPosition (just initial position - current position also works as it already negates it).