These pieces of hardware fall into several categories including fasteners, end fittings, and buckles.
Once the webbing is threaded through the fastener, the ratcheting mechanism is employed to take up the slack and tension the assembly to the necessary level.
Threaded buckles work like those found on backpacks and duffel bags for the purpose of adjusting the length of the tie down strap.
Snap buckles are also commonly found on backpacks and duffel bags to allow fastening of the strap.
While threading buckles come in metal varieties for use with tensioning fasteners like over-center and ratchet fasteners, snap buckles are often plastic and are not designed to withstand a great deal of tension.