Speaking about the theatrical and rock concert industry... In some ways the cases are standardized around being a quarter, third or half the width of a semi tr

Speaking about the theatrical and rock concert industry... In some ways the cases are standardized around being a quarter, third or half the width of a semi trailer inside width in some dimensions. So once its in a case its usually okay. Typically the cases are packed in layers based on depth and with, so if you have a set of thirds cases, they will go in a layer, if you have a cases with some odd depth, they will tend to go together. The weight of things is taken into account as well, heavy stuff tends to get packed towards the sides, near load bars (metal bars that keep the load from shifting) or the front sometimes. There are sometimes considerations for how it gets from the truck to the ground, because sometimes you get somewhere and theres no dock, or your in a smaller truck with a gate. So forklifing things is common. What goes into each case is a complicated subject. Some cases are just full of all cables of some type, or full of lights or speakers. Sometimes a case will be built around being a kit for something, or around "this is everything that goes to Greenroom x". And you have an assortment of special cases, TVs, stuff like that. You also sometimes have to consider who opens and sets up whats in a case, so rigging gear will need to be kept separate from audio gear, since those may be setup by different teams or different unions, even if that gear goes together when the show is setup. Odd sized cases and loose stuff is often packed on top or "rides on top" of larger roadcases in the truck. Often this stuff is moved from the truck onto cases before its moved into the building, since pushing a case with some extras on top is not as hard as carrying the stuff all the way in. Sometimes carts are used, not as often as I would have hoped. In many venues the people who move the cases from the show area (arena floor, stage, etc) are a separate team or separate union. If you start out in IATSE, the stagehands union in the US and Canada, you will often start by pushing boxes and generally doing physical work. But at the end of the day the truck is loaded by weight, so theres often tons of volume left over when the truck is "full" as its now at its max weight.