Final answer:
Before coupling a tractor and trailer, check and secure the kingpin, locking jaws, trailer apron, and landing gear, and ensure the electrical and air connections, fifth wheel, and release arm are in proper condition.
Step-by-step explanation:
Before coupling a tractor and trailer, it is paramount to check the condition or properly secure several aspects to ensure safety and proper operation. These include the kingpin, which should be free of damage and properly greased; the locking jaws, which must be able to close securely around the kingpin; the trailer apron, which should not have any cracks or bends; and the landing gear, which must be fully raised with no bent or broken components. Additionally, it's crucial to verify that the electrical and air connections are secure and free of damage, the fifth wheel is in good condition without excessive wear, and the release arm is properly seated and secured. All of these components play a vital role in the safe and functional coupling of a tractor and trailer.