Left Mother is the leftmost of the 3 good crack climbs in the Mothers area of the Y. Climb choss to a solid block/horn, angle left to a wedged block with good hand jams on either side. The steep crux is from here to the top and follows the leftmost crack, which is just a little larger than fingers, through an overhanging face. Fortunately, the face is highly featured with small horizontal ledges and pockets.
This climb is a good one for a trad leader near their limit, as the pro is good, the crux is short, and the fall is clean.
The 3 "Mothers" climbs are about 40' right of Beastie Crack on the north wall of the 'Y', on a clean steep section of rock. It is just a little bit before the waterfall starts.
Rack up to a 2" cam; finger size cams are especially useful, nuts are good too. Don't bring micro nuts or microcams. Save some stuff to build an anchor at the top, although there's a good block that you can sling with a long runner, or tie off trees with static line- always an iffy idea since many are dying.