A0—quick and dirty aiding, generally without etriers—is not glamorous, but it’s a handy skill to have in your repertoire, especially for moving fast. Whether it’s the Nose in one day or three, A0 gets the job done. A0 covers a wide spectrum, from hangdogging on a sport climb, to speed maneuvers on walls, to aiding through short cruxes. A0 is standard on big-wall speed ascents, and common on long free routes when you’re racing against darkness or an imminent storm — or when you’re just plain blown and trying to get the hell off.
Let’s say you’ve tried that crux move several times; it’s just not happening, and you’d rather finish your climb than beat yourself up any longer. If there’s a piece in front of you, grab it and pull through to the next good hold. If this doesn’t work, clip a sling to the piece and step into it — this will give you more reach and be less strenuous. With a single-length runner, you’ll be seriously high stepping, so make sure the piece is solid. If it blows when you’re rocking onto it, you could easily take an upside-down fall. This technique works well on short bolt ladders. If the rock is low angled, you may be able to yard through on draws with your feet smeared on the bolt hangers.
On steep rock, yarding on gear is strenuous, so don’t hesitate to fifi into a piece to rest. Even if you’re free climbing instead of pulling on gear, it’s more efficient to take a quick break than to push until your arms are completely flamed. If you don’t have a fifi hook, a biner (keylock biners are preferable because they don’t catch) clipped to your belay loop will serve the same purpose.
For speed, A0 works especially well on parallel-sided cracks, such as Boot Flake on the Nose. Sure, you might be able to free the pumpy 5.10d pitch, but A0 will leave you more energy for the summit dihedrals you’ll be facing in the evening. Try leapfrogging the same sized cam, one in each hand. Some people put their hands through the slings and use the cams in the style of leashed ice axes. Use your feet exactly as if you were free climbing, either stuffed in the crack or on face holds. A good A0 practice is to move the cams up with you, clipping fixed gear or placing nuts when you want protection. Conserving cams this way, you won’t get left in a lurch if you come across the same sized crack higher on the pitch.
Survey the rock in front of you and don’t be afraid to move back and forth frequently between free and A0. The legendary Layton Kor is an example of a climber who had an uncanny intuition for when to move from free to aid and vice versa, finding the balance that maximized that essential quality: speed. If you find yourself spending time and energy figuring out how to free a move, it will be more efficient to yard through this section (provided there is gear). On the other hand, don’t hesitate to step out of those slings and fire short sections free if they look doable. (Free climbing will always be faster than A0 as long as you keep moving.) To rest, you can either fifi into a piece or clip your lead line and call for tension. The latter works best when you want to leave one of the pieces you’ve been leapfrogging, or switch into free mode, saving you the awkwardness of clipping and unclipping. And don’t forget that it’s often best to mix it up; you might be yarding with one hand and finger jamming with the other, while one foot’s in a sling and the other’s smearing on a fixed pin or a small edge.
Consider how your second will get through an A0 section. Let’s say you yarded through a short bit of aid, but back cleaned the pro. If the rock is less than vertical, the second can batman the locked-off lead line until he reaches the next piece. Once he’s fified in and unweighted the rope, you can quickly reel in the slack. On steeper rock, the second may be able to aid through using the gear he’s cleaned. In general, a super-tight belay can expedite things when the second is A0-ing. With a little practice you’ll find A0 relatively painless. And what’s nice is that you don’t need anything more than what you’d normally carry for a free climb. When done right, A0 can speed things up, help you avoid epics, and even open access to routes that might otherwise be out of reach.