Trailer hooking 101

2009 March 18

Today we’re going to have to talk about how a trailer hooks to a tractor. All you experienced drivers out there may just want to skip it and come back tomorrow. But if I don’t explain how it all works then the non-drivers among us won’t be able to laugh at the dick-head starring in tomorrow’s post and call him mean names… like idiot and dick-head and such.

King pin under trailer

King pin under trailer

First off, this is the king pin on the bottom side of the trailer near the front edge. It is just a small cylinder attached to a steel plate which is part of the floor of the trailer.

You will notice a smaller channel on the bottom part of the king pin. This is the area that the jaws of the fifth wheel (below) actually clamp around. Then the bigger bottom edge insures that the king pin can’t bounce up and out of the jaws even if you hit very bad roads.

Also, you will notice lots of grease on the bottom of the trailer. Since the connection between tractor and trailer is basically just a steel plate sitting on a steel platform, it pays to keep lots of grease involved in the interaction. Although all that grease can be mighty messy. We once worked for a company that used king pin locks on their trailers a lot. That was a round lock that slid up on the king pin and kept the fifth wheel from fitting around it. Good god was that a mess. Every time I had to take one of those locks off I would crawl under the trailer determined to stay clean and every time I came out I had fifth wheel grease on the back of my shirt, all over my hat, in my hair and on my hands. Ugh! We still have one but don’t ever use it.

Rear view of the fifth wheel

Rear view of the fifth wheel

Ok so this is your fifth wheel on the back of your tractor. It is basically the platform that the front half of the trailer rides on. It is also the pivot point when making a turn. And when the king pin is connected to the fifth wheel it provides the “pull point” or whatever you would like to call the single point where the tractor exerts the force required to drag the trailer around the country.

Right off the top of my head, I can’t for the life of me remember what I was intending to draw your attention to with arrow number one. Maybe I was just going to reinforce that the area arrow number one is pointing at is the actual surface the trailer sits on. Maybe I just like drawing arrows. Who knows? We should probably move on to arrow number two since I know why I made that one.

Arrow number two is the channel the king pin slides through until it engages the jaws to clamp down around it. If you look at the end of the channel you can see the jaws although they are not engaged in that picture. You might think it’s kinda hard to connect trailer and tractor. I know when I first started out in trucking school that was one of the things I was most nervous about. It is surprisingly pretty easy. If you’ll notice, the channel the king pin travels is wider at the beginning and sort of funnels down to the jaw area. So even if you aren’t lined up perfectly the trailer will usually adjust as you back the tractor underneath it.

Important rules about hooking up to the trailer:

1.  Make sure the trailer is actually sitting on the fifth wheel. There should be no gap between them.

2.  Back slowly under the trailer but with enough force that you engage the fifth wheel jaws. In almost every truck I’ve ever driven you can actually hear the jaws engage, but once you are connected you should still do a tug test. A tug test is simply putting the tractor in a low forward gear and easing off the brake. If properly connected, the tractor will pull forward but be unable to move because the trailer brakes are still engaged.

3.  Once you set the tractor parking brake and get out of the truck you should actually duck under the trailer and visually double check that there is no gap between the fifth wheel and the trailer. You should also look to make sure the fifth wheel jaws are actually locked in place around the king pin.

4.  If the trailer is properly secured, go ahead and hook up your pigtail and air lines and raise the trailer’s landing gear. Then proceed to pre-trip the trailer.

It may sound like a lot, but it really takes very little time. I can do a complete drop-and-hook including a good inspection of the new trailer in less than fifteen minutes. And I think we’ve more than adequately covered my lazy streak in past posts, so I assume you will all understand what I mean when I say there really isn’t any excuse for not doing it properly. I mean if I’m willing to do if faithfully every single time how hard can it be, right?

Besides… there are consequences and repercussions to not hooking up properly. Tune in tomorrow for a fifth wheel related laugh.

9 Responses
  1. 2009 March 18

    I am now fully prepared to do two things:
    1) Laugh tomorrow about the idiot dick-head
    2) Find a way to make those arrow thingys. I don’t think I would use it on my blog, but do have a few annoying people who email me sometimes. I would like to respond with a simple arrow pointed at the words, “You are annoying.” And a few other things that go back to that whole idiot dick-head idea.

    • 2009 July 22
      Brian Shaw permalink

      I was pulling a load for Werner last year on I-40.I had the fifth wheel in the shop twice to be looked at they said it was ok.It wasn’t,Trailer came off at 45 mph.Thank God their was know one behind me for at least 10 miles.

      • 2009 July 22


        I hear you — mechanical failure is a constant fear of mine. What can you do about it but keep trying to convince the shop guys that there is something wrong? Then it’s up to them to do the right thing.

        I’m glad nobody was behind you. I was once driving behind a truck pulling Fedex doubles when the rear pup broke loose. It still connected by the chain, but that was it. That pup went wild going every which way. The Fedex guy was all over the road trying to get the pup back under control so he could get to the shoulder.

        Luckily, Stace and I are big fans of following distance so we were ok, but I looked in my mirror and saw there were about five four-wheelers coming up fast behind us. I put my flashers on and started weaving big loose lines from one shoulder to the other trying to freak them out and make them back off. It worked and they all stayed behind me as I slowed down. So we were all able to give FedEx plenty of room to get the thing under control and off on the shoulder.

        In the end it all worked out ok and nobody got hurt, but that was a scary couple of minutes. After FedEx got stopped, we walked back and looked and the steel loop that they hook the dolly to had just split. Never saw anything like it.

  2. 2009 March 18

    We don’t drop and hook like you guys do, but Ed has a little trick for using the king pin lock and not getting grease on his hands…

    He always takes a plastic Walmart bag and puts it over the pin, then puts the cuff on, then locks it. When he takes it off, the grease is not on the lock and he just throws the bag away.

    I don’t know how he keeps the grease off the rest of his body though – maybe he played that limbo game a lot when he was a kid.

    Although, he stays surprisingly clean no matter what he does on the truck. He can load the whole trailer and not get a speck of dirt on him. Me? I come out to help him, pick up a bungee or two and wind up with dirt smudges on every piece of clothing and grease somewhere on my body. How???

  3. 2009 March 18

    You tease! lol. I can’t wait to see tomorrows post! lol.

    I can’t believe that you have to do all that. It seems like truckers really have to be mechanically inclined and smart! Always alert! Seriously, not many people could actually do what you do. Seems like a really tough job to me. I have a whole new appreciation for you truckin people!

    Oh, ever drive through Euclid Ohio on I90? I hear they are thinking of putting those speeding camera’s along that little stretch of highway! Yes! On the HIGHWAY! Dumbasses.

  4. 2009 March 18
    limericc permalink

    Hey ladies. Just found your blog, enjoying it a great deal. I instruct CDL class, and love forwarding your stories and lessons to them. Keep up the good work.

  5. 2009 March 18

    First you’re on a radio show and now you have a CDL instructor forwarding your blog posts??? What about meeeeeeeee???

    Doesn’t anyone want to know how to bake a cake in a truck?? Does not a soul care that I have a bib that says “I’m as cute as a ButterBurger is delicious”??

    I think I’m gonna cry. LOL

  6. 2009 March 18



    Well you were in the Pilot magazine. As a matter of fact you’ve been in it twice as I recall.

    And you’re like a million times more cute than I am so the bib is fitting. I would have to get one that said “I look like Hedon’s socks smell” or something similar. :)

    Oh and the WalMart bag on the king pin lock — ED! IS! A! GENIUS! Seriously, that is just brilliant. Don’t you sometimes hate when someone else has such an inspired idea and you wonder how it is that you didn’t think of it yourself? But at the same time you just really — really — enjoy the evidence of the other person’s superior brain power. It makes me pissed off and extremely happy at the same time when other people have really awesome ideas. So tell Ed “thanks” and “suck it” from me. :)

  7. 2009 March 18


    I do like drawing the arrows. I do them on a seperate layer of the picture so I can add a whole bunch then I end up taking some out before I post the picture so they don’t block everything. :)



    Ugh! I always get crap all over me, too. Seems like everytime I step out of the truck I manage to either get grease of some variety all over myself or rip a hole in my shirt. Luckily all I ever wear are $5 t-shirts from WalMart so I end up just throwing several away every month. It’s got to be tougher on you since I’ve noticed you have a much higher class wardrobe.



    You don’t have to be too terribly mechanically inclined but I suppose it probably does make life a little easier if you are. I have always been comfortable in that arena and I’m sure it has made my life easier.

    You do have to be constantly alert. Seriously. The truth is that one slip of attention could have devastating consequences — and no one wants that. I keep a set routine in hooking and unhooking and if it gets interrupted for any reason I will often go back and double check each step from the beginning to make sure all is in order.

    I agree that trucking isn’t a good fit for everyone. Some people do find it too hard. It is often hard, but it has valuable benefits that are more important for me. Like I could never ever survive in an office. Trucking might be tough but it’s almost always an adventure… oh sure… it might be a hideous adventure that requires a couple of National Guard guys to ride standing on your running boards for 15 miles… but even that hell was an adventure. :)



    Welcome! Glad you’re enjoying stuff around here. Also glad you’re training up the next generation so to speak. If nothing else I could probably keep them amply supplied with “what not to do” stories based on all the stupid things I’ve done out here on the road. :) Hope we can help them get as smooth a start out here as possible.

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