.  Check the position of the tractor by using both outside mirrors and by looking down both sides of the trailer. Step 4. Back slowly l   Back slowly until the fifth wheel just touches the trailer. Step 5. Secure tractor l l l Apply  the  parking  brake. Place the manual transmission in neutral; if an automatic  transmission,  place  in  park. Place  wheel  chocks. Step 6. Check height of trailer .    The trailer should be low enough to allow it to be raised slightly by the tractor when the tractor is backed under it. Raise or lower the trailer as needed. CAUTION If the trailer is too low, the tractor may  strike  and  cause  unnecessary damage to both the rear of the tractor and the nose of the trailer. If the trailer is too high, it may not couple correctly. . Ensure the kingpin and fifth wheel are aligned. Step 7. Connect air lines to trailer l l l l Inspect  rubber  grommets  in  the  glad  hands  for wear and tear. Connect the tractor emergency air line to the trailer  emergency  glad  hands. Connect the tractor service air line to the trailer service  glad  hands. Ensure air lines are safely supported so they cannot be crushed or caught while the tractor is backing under the trailer. Step 8. Supply air to trailer l From the cab, push in the “air supply” knob to supply air to the trailer brake system. Military tractors are sometimes equipped with shutoff l l l valves that must be opened to supply air to the trailer brake system. Check the air pressure gauge and wait until the air pressure is normal. Apply  and  release  trailer  brakes,  listen  for  the sound of the trailer brakes being applied and released. You should hear the brakes move when applied  and  air  escape  when  the  brakes  are released. Check the air pressure gauge for signs of major air loss. Step 9. Lock trailer brakes .    Pull out the “air supply” knob or apply the trailer hand valve on the steering column to lock the trailer  brakes. Step 10. Back under the trailer l l l Use the lowest reverse gear. Back the tractor under the trailer until the kingpin is locked into the fifth wheel. Pull the tractor gently forward while the trailer brakes are still engaged ensuring the trailer kingpin is locked into the locking jaws of the fifth wheel. Step 11. Inspect coupling to .   Place the transmission in neutral, if manual; in park, if an automatic transmission. .   Engage parking brakes. .   Disengage the trailer hand valve. NOTE: Depending on your location, you may want shut off the engine and take the key with you to prevent someone from moving the truck while you are under it. .   Inspect the area around the fifth wheel. Make sure there is no gap between the upper and lower fifth wheel. If there is a gap, something is wrong. The kingpin may be on top of the closed locking jaws; if so, the trailer can come loose easily. 7-15