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.
As with the 4:1 and 6:1, the 9:1 can be rigged as either a simple or compound system. Simple 9:1 systems are completely impractical. 'Nuff said. Compound 9:1 systems are a piece of cake if you already know how to rig a 3:1.
Refer to the overview on raising systems to learn more about mechanical advantage systems.
By definition, compound systems have one simple system connected to another simple system. In this case, we've stacked a 3:1 on a 3:1.
Although this is a compound system, you can see it was rigged using a single rope (we changed the rope's color from yellow to orange to show where the two 3:1 systems meet).
Notice that the capture Prusiks are on the rope coming from the load and not on the upper anchor.
Creating a compound 9:1 on staggered anchors, as shown here, requires a relatively large rigging area, but it is much easier to visualize the two 3:1 systems and it is easier to reset the systems.