On the boulder of Incassable. Sitstart completely left, traverse to the right on slopers, downclimb 1m after the angle, traverse with top holds in the tunnel up to the big hold and make the back traverse to the starting point.
From the parking lot of the equestrian centre, follow La Route d'Arbonne à Achères for 250m; the boulder is 30m above, shortly after a TMF mark on a tree.