How to Couple a Trailer (and Avoid a High Hitch)
Updated June 2026
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Coupling looks simple, but getting it wrong is one of the most dangerous rookie mistakes. The big one is a high hitch (a "high hook") — where the fifth wheel slides under the trailer without the kingpin locking in. It looks connected, but the trailer can drop or come loose. Here's how to do it right, every time.
What a high hitch is
If the trailer is sitting too high, the fifth wheel skids underneath the trailer's apron (the flat plate around the kingpin) instead of catching it. The locking jaws close on air — the kingpin never dropped in. It can look coupled from the seat, but it isn't locked. The fix is all about trailer height and checking.
Step-by-step coupling
- Secure the tractor and trailer. Chock the trailer wheels or make sure its brakes are set.
- Set the trailer height. Use the landing gear to lower the trailer so it's a little low — the fifth wheel should touch and lift the trailer slightly as you back under. Too high = high hitch. Too low = you'll hit the trailer nose.
- Line up. Center the tractor so the fifth wheel is straight in line with the kingpin. Back straight, slowly.
- Back under. Ease back until the fifth wheel just touches the trailer — confirm it's catching the apron and raising the trailer, not sliding under it. Then continue back until you hear/feel the kingpin lock into the jaws.
- Tug test. With the trailer brakes locked, pull gently forward against the kingpin. The tractor should stay hooked. If it slides out — it wasn't locked. Redo it.
- Get under and look. With a flashlight, confirm the locking jaws are closed around the shank of the kingpin, and there is no gap between the fifth wheel and the trailer apron. A gap means a high hitch — pull out, lower the trailer, and try again.
- Check the release arm is seated in the locked position and the safety latch is engaged.
- Connect the lines. Hook up the air lines (glad hands) and electrical cord; check for the right connections and no leaks.
- Raise the landing gear fully — last. Only after you've confirmed a solid lock. Secure the crank handle.
The rule to remember
Never trust your eyes from the cab. Tug test + flashlight check, every single time. No gap, jaws locked around the kingpin. That one habit prevents dropped trailers.
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Frequently asked questions
What is high-hooking?
A high hitch (high hook) is when the trailer is too high and the fifth wheel slides under the apron without the kingpin locking into the jaws — it looks coupled but isn't secured.
How do I know the trailer is locked?
Do a tug test (pull forward against locked trailer brakes), then get under with a flashlight and confirm the jaws are closed around the kingpin with no gap between the fifth wheel and trailer.