There is a dark art that not many climbers talk about, and even fewer practice - rope soloing.
Climbing terms get confusing, especially when they overlap. The term soloing means climbing alone. Free Soloing, like what Alex Honnold is known (and won an oscar) for, means climbing without any protection at all, usually wearing just climbing shoes and a chalk bag. This is not to be confused with free climbing - where one uses just the holds on the wall to make upward progress, differentiated from aid climbing which is sort of the all-bets-are-off beast mode where you can place a cam or bolt and use that to hoist yourself higher, sometimes to place another cam or bolt. Things only gets more confusing as we get into leading, following, onsight vs. flash vs. redpoint or pinkpoint, and the list goes on.
So rope soloing.
In this practice, the biggest differentiator is between lead rope soloing and toprope soloing. To do the latter one needs access to the top of where you’re climbing to in order to set an anchor, which at many crags is a great option. If there’s not ready access to the top, one needs to lead climb to “get the rope up there”.
Most lead climbers will have a belayer, someone to pay out the rope for them as upgward progress is made, and to lock off the rope and “catch” the leader on their gear in the case of a fall. If they come off the rock, the leader will fall as far as their last piece of protection is from their waist where rope is tied into the harness, then that same distance again, plus the additional 2-5 feet or so of slack that might be in the system. Generally this isn’t more than a dozen feet or so in the worst case.
As a rope soloist, you won’t have a belayer, so another system needs to be in place to make that catch in the case of a fall.
There are a handful of devices for this, most of them rely on a camming mechanism like Petzl’s GriGri or Traxion, which pinches the rope. This device needs to be attached to the leader, and the rope run through it and anchored to the ground somehow. If the leader falls, they will fall to their last piece, the same distance again as before, and then the tension in the rope will lock the camming mechanism, the anchor takes the brunt of the fall, and the climber is arrested. Plus whatever slack is in the system.
There’s another type of device called a Silent Partner that was manufactured by a company Rock Exotica for a few years, but discontinued due to lack of demand. These are mythical devices that demand a steep price on the secondary market since they were discontinued, and have a unique mechanism. Instead of a camming action, there’s a centrifugal clutch inside, much like a car seat belt. When the right knot (a clove hitch) is tied around a drum, it will let the rope travel along the device so long as it’s pulled slowly, like the case of a climber moving upwards. If the rope gets pulled fast,like in the event of a leader fall, the device locks up and stops the rope from passing through at all, catching the leader.
There are a few advantages to this device, including catching a fall no matter the orientation of the leader, unlike a camming device which needs to be in the correct orientation in order to lock on the rope.
If a picture is worth a thousand words than a video must be worth at least that many. Here’s a video of me climbing a spire in the St. Vrain Canyon that has no access to get the rope to the top without a leader taking some risk, and on this particular day I was left without a partner so I did it - rope solo style.
Take a look.