El Potrero Chico’s rugged cliffs draw climbers worldwide with their commanding walls and endless vertical puzzles. Among these stands Ass Hat's Chossy Dihedral, a raw, one-pitch sport climb carved into a moss-covered left-facing dihedral that demands respect as much as effort. Unlike the polished faces that attract the crowd, this line embraces the roadside grit of climbing—where moss clings stubbornly to fractured rock and the loose holds challenge more than just your technique.

The climb unfolds just right of the main gully, inviting you into a confounding patch of damp stone and inevitable dirt. The moss acts like a veil, masking fragile flakes and questionable grips. As you ascend, the dihedral’s texture shifts; the lower section offers tenuous but passable holds, but above, the rock fragments easily beneath your touch, testing your nerve and route reading skills. It’s a battle against nature’s reclaiming hand—every move is calculated, every hold weighed.

At roughly 100 feet, it’s a moderate endurance pitch by length, but the precarious surface transforms the 5.10+ rating into a grit-heavy challenge with a mental edge. The bolted anchors are somewhat outdated, with the current belay fashioned as a precarious American Death Triangle on a small ledge. Bringing webbing to create a safer anchor replacement is strongly advised if you plan to finish the route, though many climbers choose to bypass the upper section entirely.

Approach the climb from the base of The Dihedrals, where steep footpaths cut through desert scrub and scrubby trees—expect a short but uneven hike that sets the tone for a day carved in roughness. The arid air contrasts sharply with the moss that saturates the dihedral’s shadows, a reminder of hidden microclimates among the otherwise dry canyon walls.

While some might shy away from the dirtiest pitch at EPC, it holds a certain grit-driven appeal for those who thrive on confronting climbing’s rawest elements. Gear-wise, standard sport rack with an emphasis on quickdraws is sufficient, but patience and steady footwork surpass pure gear reliance here. Sticky rubber shoes and a firm grip are your most valuable tools.

Local advice: avoid climbing this route after rain or heavy dew to reduce moss slipperiness and rock breakage. Time your ascent for morning hours when the sun dries the surface but leaves the approach trail shaded and cool. Stay vigilant of loose rock higher up and always test holds before transferring weight. Finally, descending involves switching your attention to safely leaving the technical discomfort behind, with a return down steep scree that demands caution.

Ass Hat’s Chossy Dihedral is no polished gem—it’s an unfiltered, tactile experience that tests your climbing intuition on one of Mexico’s most storied walls. If you’re after smooth sport routes, look elsewhere. But if you welcome a gritty, mental contest against nature’s slow unraveling, this climb invites you to measure your resolve against a truly dirty challenge.