You've seen the pet crates. They're used to house train dogs, or for quick trips to the veterinary hospital or clinic for cats. Some are made for quick assembly or to be able to get your pet inside without too much of a fight.
Are all crates the same? No! Crates used for air travel as checked baggage or via cargo must be made of a rigid material (plastic, metal, or wood). It must have a metal door, a door locking mechanism, and if it has top and bottom sections, the sections must be held together with threaded nuts and bolts.
As an example, the pet creates in the photos, were used to transport cats for a veterinary visit. These crates would not be acceptable for transport as checked baggage or via cargo.