This is a classic Chuck Pratt testpiece - a must-do for anyone interested in historic wide cracks. The crux climbs more like a chimney than an offwidth, so throwing a toprope on Moby Dick, Ahab is good training for it. The Slack Left requires less endurance then Ahab, but the short crux section is a step up in terms of pure difficulty.
Pitch 1 (5.9) - Start up the double thin cracks in a corner. They are often filled with munge, so you may need to dig them out to place pro. Climb up through the tree to reach the start of an offwidth. Fear not, there is a crack inside the offwidth which can be jammed and sidepulled. Eventually the crack will widen to a chimney which is a bit dirty. A short section of chimney ends the pitch. There are two options for the belay. Either sit on the ledge on the right wall of the dihedral, or belay in the back of the chimney off two pitons. I chose the ledge because it seemed more comfortable, but you can also make your choice based on whether you wish to belay in the sun or the shade.
Pitch 2 (5.8) - Continue up the chimney towards the roof. Small cams protect in the back. At the roof traverse left and climb up a short loose section before rejoining the corner. Alternatively, if you're feeling burley you can climb straight through the roof using the 5" crack (probably at least 5.10). From here there's another section of offwidth up the dihedral, and same as p1 there's a crack within the crack, making the climbing easy. Belay at two pitons and gear on a ledge left of the corner.
Pitch 3 (5.10b) - This is the pitch that separates the men from the boys. The first two pitches are somewhat easy and average in quality. The final pitch is fiercely difficult and absolutely fantastic. If you're not feeling up for it, you can always tunnel through to the final pitch of The Slack Center, and finish on a pitch of 5.8, making for the most moderate way to climb to the top of The Slack. Otherwise, collect yourself and begin up the long chimney. I stayed near the edge because there was water running down the chimney further back. There are lots of good edges which make the climbing very easy (5.5 - 5.6). There's not really any pro, but if this section doesn't feel totally casual you're probably way in over your head. No matter what path you choose through the chimney, you'll eventually be forced to a inverted V-slot near the edge. A #5 Camalot protects the initial squeeze chimney moves and a #4 nicely protects the crux where you must partially exit the chimney. Like many wide cracks, it's easy to stay stuck in place, but making upward progress is very strenuous. The crux is less than a body length but you must fight for every inch. Resist the urge to wedge your hips in the chimney to rest. Once you're wedged, it's very difficult to get moving again.
After the crux you gain a stance on a sloping ledge, but it's not quite over yet. The final obstacle is an overhanging flake that is *just* too tight to squeeze behind. The Don Reid guidebooks marks this section as "5.9" on the topo. Maybe I was just so exhausted from the crux below, but this felt more like a 5.9+, of the very most sandbagged type imaginable. Being a small person is extremely helpful here. This will be very difficult (possibly even the crux?) for really big dudes. It's also more difficult to protect than the lower crux. I was able to squeeze my chest in a short ways up and reach in deep to place a #6 Camalot. If you're too big to squeeze in here and reach back for pro, this could be very hard to protect without Valley Giants or Big Bros. However you manage, wiggle and squirm your way up the thing until the crack widens enough to finally take a deep breath. Just another 20 feet of easy wide chimney with lots of features and you'll be mantling on to the summit of The Slack - a very small feature compared to the behemoth it leans against, but an excellent climb and proud accomplishment nonetheless.
Descent - Rappel with two ropes. I prefer to swing over to the anchors atop p3 of La Escula, rather than rap the route and deal with old pitons and webbing. There's a tree that might snag your ropes, but it's easy to lead over and fix the problem. From p3 of La Escula, believe it or not, just one more rappel (with 2 60m ropes) gets you back to the ground.
The route follows the large left-facing corner up to the top of The Slack. It starts just a few feet to the left of The Slack Center and Sacherer Cracker.
P3 of this route is older brother of Ahab. Harder and longer (~140 of wide) Do not underestimate first 80 feet of 5.7 chimney with only one small placement in the middle(red purple alien size). Probably blue bigbro should work there ( not sure) Crux come at 100 feet up the pitch - inverted overhanging V slot felt harder than Ahab and come where slot become too narrow for chicken wing. Here you struggle for every inch for 3 feet. Second crux follow immediately after the good rest- overhanging tight flare with flake- call in the book 5.9- can be well rated 10b and felt not much easier than lower one- also too tight for chicken wing make it hard.