Webbing - What is it?
Webbing is what lays the foundation for rappelling anchors. They have other secondary uses but for Canyoneering, but building anchors is the primary reason.
Webbing is bought in Climbing stores "by the foot" and that's what the community recommends on how to buy it as you can get custom lengths.
There are two types of webbing that is manufactured: "Tubular Webbing" and "Flat webbing".
"Flat webbing" is just a pattern of weaved nylon fibers that has a high-tensile strength! Due to the nature of it being flat, if it gets dragged across an edge or sharp-rocks its stiffness allows it to tear. Not too easily, but enough to cause everyone to "inspect" it every time at every rappel.
"Tubular webbing" is similar to "flat webbing" but uses a tube that lies flat but has the benefits of having the wrap-around webbing as it increases the strength. SterlingRope.com says that one-inch tubular webbing has a minimum breaking strength of 4000-lbs per inch. It can be bought with a higher-rating up to 9800-lbs per inch.
Webbing is made primarily out of Nylon material. It is usually 100% Nylon but have seen other mixes, such as 90% nylon and 10% polyester. I've heard of webbing being made from Kevlar, but it is quite expensive! But for canyoneering purposes, 100% Nylon is all you need (until the next advancement in the sport comes along).
They come in various shapes and sizes and colors. The community standard when it comes to size is: 1 inch (or 25 mm). You can buy thicker sizes such as 2 inches, but it is not necessary. The comm-standard (and for some N.P. it is a requirement) for colors is "earth-tone". Meaning black, brown, tan. Please DO NOT get ones that are are blue, pink, white, red, etc. Yes, they are easier to spot, but the purpose of the color is to have the canyon look as "pristine" as possible. In fact, some rappels are public facing and nothing ruins a great shot of an arch or waterfall than having some brightly-colored webbing dangling off on it at the top.
There are several iterations of webbing such as specs for the Military, Rock Climbing and Commercial grade uses. All will suffice along as it has a breaking point of at least 4000-lbs per inch.
In canyoneering, when you come up to a cliff or drop that needs to be rappelled, you will look for "natural anchors" (such as rocks, boulders, trees, roots, etc.) or "man-made anchors" to tie your webbing around. The "Water Knot" is the knot that you will be tieing your webbing around on these anchors.
Remember, that canyon conditions change frequently! And you will need to rebuild anchors (a lot!). Don't ASSUME that a water knot is safe just because its laying there. Examine it! Being in the sun all day will make it brittle and reduce it's overall strength. And webbing that's been submerged all day (and for many weeks) will need to be changed as well. It will become water-logged and saturated and again reduce its strength.
Strong when used correctly.
Fairly inexpensive when bought in a spool and the cost is shared among your party.
You will be replacing this often so cost can add up. But I see that as a "price to play".
Webbing must be examined at every rappel, every time.
Look for frayed, cracked, stiff, cut, sun-bleached webbing. Replace it with a new strand.
Canyoneering Usage Examples:
Coming to a cliff that has no anchors visible to rappel from. You would sling a "natural anchor" using webbing. This mean wrapping around a tree trunk, tree roots, a giant boulder, or even an advanced anchor such as a "deadman" anchor where a rock is buried in the ground. Webbing is the means to "sling" or build that anchor.
Recommended Length: 30 feet/person
Recommended Colors: "Earth-tone" IE Black, Brown, Tan. NOT Red, Orange, Blue, Green, etc.
Recommended Width-Size: 1-inch width (or 25 mm)
Buy from REI.com: Webbing
Buy from CanyoneeringUSA.com: Webbing