Many people who do Air logistics have a rather vague understanding of consolidation. A rough understanding is that before loading, the cargo will be firstly loaded on a main PMP/PMC of certain specification, after that all cargo can only be totally loaded into the Aircraft cabin. (Similar to shipping container). Cargo will be consolidated firstly into the PMP/PMC based on certain rules, after that all cargo can only be loaded into the belly of the air craft cabin.
The PMP/PMC have certain specifications, including high PMC (318*244) and short PMC (318*224), etc. You can easily find these kinds of knowledge on the websites of airlines. As for the PMP/PMC requirements, it depends on the space you need. If you get the short PMC, the max height can be 1.6M. (generally, the short PMC can be loaded with 8-10 cbm cargo, which depends on pallet or loose cartons), the middle PMP/PMC is generally 2.4M height for the 747 freighter, and 1.6M for the MD11 freighter, depending on the air craft type and different airline requirements. The PMP/PMC is the tool specially used by airlines to gather the cargo, and each PMP/PMC has its own number so that you can track the cargo on it.
Consolidation actually includes the action of packing, which is to put the goods on a ULD, it will follow some rules, for example the density cargo often be put on the bottom above the PMP/PMC, the volume cargo often on the upper side above the density cargo. The short/middle/high PMP/PMC and each have certain max weight/cbm. The loading staff console all the cargo onto the PMP/PMC firstly then cover the cargo with an arch mesh to make a quick loading and unloading during the transportation. It must to balance the weight /volume, and the tracking number must be marked on the loading list. With this list, the staff will move the prepare PMP/PMC to a crate location in order to loading it into the certain place of the air craft. Mostly except some very small air plane do not have PMP/PMC, generally almost all the air craft have it for loading the cargo.
You must not think that boarding is a very simple job! consolidation is not only a physical job, but also a technical job! An airplane must be balanced to take off. How to use every inch of space reasonably, how to accurately use each ULD/PMC, and how to match it to maximize benefits requires the workers to study step by step in practice, and finally form a refined operation specification.