Part of me is hesitant to classify this as an essential knot, but the majority of me thinks it is an overlooked knot and needs to be used more.
I love this knot not only as is it is easy to tie, but more importantly it ISOLATES both strands of the rope.
What this means is that one person can rappel SRT (Single Rope-Technique) independently from the other person. Other knots do NOT isolate the rope strands like this and doesn't allow for two rappellers at the same time.
The primary scenario for when this is used in canyoneering is for sequencing. This will speed up rappels so that two people can rappel at the same time and NOT affect the other person, including their weight or size. For example: whether that person is 300 lbs and the other person is 60 lbs, they will NOT affect each other.
CRITICAL NOTE - this hitch HAS to be untied before the last rappeller goes! If you don't, you will need to ASCEND the rope (hopefully you have the experience!) and untie it, otherwise you are stuck!
If practiced and used in canyons where there are numerous rappels, or you are bringing a large group, or you have a mix group of beginners and experts, the Stone Hitch can drastically save critical daylight time, as this is the biggest time-waster in canyons.
Allows for two people at the same time to rappel independently of each other.
Allows for releasable toggles to be used (such as FiddleStick/Smooth Operator/etc.)
In conjuction with other practices, this is used in "Ghosting" techniques for Canyoneering.
Must have an extra carabiner (or releasable toggle) to use.
This hitch HAS to be untied before the last rappeller goes! If you don't, you will need to ASCEND the rope (hopefully you have the experience!) and untie it, otherwise you are stuck!
Canyoneering Usage Examples:
CanyoneeringUSA.com: The Stone Knot (aka Stein Knot): A Canyoneering Secret Weapon
Below, I show you three ways on how to tie the knot, via:
2) GIF (animated picture that repeats itself with no-end)
3) Video (from Canyoneering101 YouTube Channel)