Rig plans and why they are essential: 

A rigging plan is important as it shows the engineer where the fixtures need to be rigged, this is also important due to the safety aspect and planning correctly as you must think about whether they may be enough power. You also may need to consider how the rig works, such as whether it uses integrated wired bars and whether they are 13amp, 15amp or 16amp powered. The lanterns are hung in the rig, according to how it's drawn on the plan. They need to know the positions of the lanterns what lanterns are being used and how they will be powered. 

It is also important on how the set is being used to make sure no lanterns are in the way or obstructing areas that are needed. 

They may need to know if intelligent fixtures are being used as they must have hard power as they are non-dim fixtures