What must you do before detaching a semitrailer?

Before detaching a semitrailer, it is essential to follow specific steps to ensure safety and prevent damage. First, you must lock the wheels of the semitrailer and extend the supporting legs to ensure the trailer remains stable and will not move or tip over when detached. Next, disconnect all the hose and cable connectors between the truck and the trailer, as these control systems like brakes, lights, and air supply. Finally, release the coupling lock and open the hitching device of the fifth wheel to physically separate the trailer from the truck. Doing all these steps in the correct order is required so that the detachment process is safe and nothing is damaged or left unsecured.