You can find this boulder on the line between Le Toit Triangulaire 6a ( close to Le Bilboquet d'Isatis, blue n°50) and Luna 6a. Closer to Luna,just in front of it. You start in sitstart position and exit in L'Échine. There are no notes of using only the arete, so I chose this beta (2 hand on the rock itself). Easy climb up after you grab the top edge.