The "critical point test" (aka "scissors test") requires that if any one item fails, nobody should be injured.
A "bend" is a knot that joins two ropes.
A "hitch" is a type of knot that must be tied around another object.
The "whistle test" requires that if all rescuers let go, nobody should be injured.
It is important to know how to convert between kilograms, kilonewtons, and pounds.
You can use this nifty calculator (which adheres to the mass and force terminology), or you can use the following approximations.
Most climbing and rescue gear is rated in kilonewtons, so it's essential that you can either think in kilonewtons or quickly convert between kilonewtons and your native units. A memory aid for pound-handicapped rescuers is to think of a friend who weighs approximately 225 pounds and nickname them "Kilonewton." Then when you see a piece of equipment rated at, for example, 26 kN, you'll quickly know that gear could hold 26 of your friends.
All illustrations on this website were created using the vRigger software.