When reading this passage I thought it refered to all walks they had taken together, even back at Uppercross, walking through the fields and "jumping her from the stiles. At dictionary.com, a Stiles is said to be a set or series of steps for crossing a fence or wall. or A turnstile. I do not know if the cobb has a stiles so I could be wrong. The fact that CW thinks the hardness of the pavement is too great also does not make me think he has jumped her down at this location before.