The concept of the mod is really simple, it is the same as other props mods in other games. The hiders can disguise as objects, and hide on the map.
This mod is my favorite CoD4 mod. I play it almost everyday with my classmates, it doesn't have annoying bugs and finally, it's not another zombie mod. It's sometimes surprising how it's possible to hide ; a friend of mine succeeded in hiding as a delivery truck in Shipment by going in a container, and having me disguised as a sheetmetal to make a false end of container and cover him XD