The truck's coils are supported by a coil well. The trough-shaped recess is typically found running the length of the loading floor. A coil well's main function is to hold coils in place. Due to their round shape and weight, these coils can weigh several tonnes and can be difficult to secure with belts or wedges alone.
The circular coils are secured against lateral slippage if they are lowered into a coil well. Coil wells can be covered with planks or boards when not in use, allowing the trailer to function like a typical semi-trailer.