Intro to Rigging
"Rigging" refers to the way we setup our rappelling systems.
The three found in canyoneering are are:
1) Releasable/Contingency (Preferred!)
This allows people to rappel like normal, but if a problem was to arise: hair gets stuck, unable to rappel further, etc. This allows you to simply convert the rigging to a lowering system. There is no extra gear required to make that happen.
The two most common Blocks are:
Figure 8 Block
Totem 8 Block
2) Rope-Blocked Systems
A rope-blocked system is typically found where a knot (in this case, a clove hitch/triple clove hitch) is used to block off one side of the anchor while you rappel off the other.
It is VITAL that you know which side to rappel on.
Dozens of accidents have happened because people have rappelled off the wrong side and since there was no rope-block, it was as if they just fell from the top of the rappel! Some lived, others died.
It takes 5 extra seconds to make sure you are rappelling on the blocked-side of the rope.
Clove Hitch/Triple Clove Hitch
3) Toss N' Go
Toss N' Go is where you go "double strand", which means that there is no rope-block or contingency point involved. It is simply finding the middle of the rope and rappelling on both strands of the rope to the bottom.
This is a very fast way to rappel, but does not allow for contingency! If someones hair gets stuck or something else happens to the rappeller, you will need to deploy a second rope (hopefully you brought one). Toss N' Go is usually setup for small rappels where the "penalty points" isn't high.
Blocking off one of the strands and rappelling on just one isn't a toss n go, but has now converted to a rope-blocked system.
My suggestion is to do this on short rappels, usually under 50 feet.