There are several simple things you can do to assess your trailer's safety at home.

Has it been a while since you hooked up your truck and trailer?  Don't just assume your rig is roadworthy; check it out before you load up your horses and head down the highway.  Of course a thorough annual inspection by a licensed mechanic is a good idea, but there are several simple things you can do to assess your trailer's safety at home.  Here's a trailer inspection even the mechanically inept can do.

   Start by donning your grungy barn-mucking clothes and giving your trailer a bath – inside, outside, and underneath – to expose any flaws that may be hiding under road grime and mud. 

    Check your wheels and crawl under the trailer with a flashlight and a long, sharp screwdriver.  Probe all the metal parts of the undercarriage with your screwdriver, looking for cracks and rusting, especially at the joints and rear cross members where urine and manure tend to collect and eat away at the metal.  Poke at the floorboards, as well, to see if they need replacing.  Solid boards are firm and hard, and don't give way to the screwdriver; rotted boards will have the consistency of cork. 

    Shine your flashlight over the suspension and the wiring, and note anything that looks cracked or broken.  If the wiring is hanging down, it may snag as you drive down a potholed dirt road or through the hayfield parking lot at your next show.  Try to readjust the wiring, or note it as something a repairman should fix.  Frayed or broken wires will need to be replaced.

    Inspect your tires.  If your trailer has been sitting in one spot for a while, more than likely the tires will be soft, and the rubber may have suffered from exposure to the weather.  Check for tears, bulges, or cracks, or signs of a puncture, and take a close look at the treads.  Use a tire gauge to make sure they are inflated to the recommended pressure.  The correct pressure should be printed on the sidewall.  Check your spare tire to make sure it’s in good condition.

    Walk around your trailer and look for signs of rust along the seams between the trailer tongue and the body, as well as along the roof seams.  If you have a steel trailer, rust will be a perennial problem, and you'll probably need to repaint every five or six years to keep ahead of it.  Even aluminum trailers sometimes have steel frames, so check carefully along the edges of the side body panels.  Excessive rust may mean you have a structural separation that a good kick or body check from your horse could turn into a deathtrap.  If there are areas on the inside of your trailer where the bare steel is exposed, you can protect them with a coating of the material used to undercoat cars.

    Open the doors, checking that the hinges on the front escape door still work smoothly, and that the ramp or rear doors (if you have a step-up trailer) swing without grinding or squealing.  Your trailer should look straight and square, with nothing out of alignment.  Have a good look inside with your flashlight, if necessary.  Are your roof supports in good condition?  Do all the latches, chest bars, butt chains or bars, and pins for your partition fit together smoothly?  Do the vents and/or windows still open and close properly?  Are there any splinters, protruding screws or rivets, loose wires, sharp edges, or other hazards on which your horse could injure himself? 

    From the inside, brace your hands against the sides of the trailer and try to twist or move the metal shell.  If there's any give at all from the paltry pressure applied by a human, imagine what your horse can do to it.  And have a good jump on your ramp (if you have one).  The wood used in ramp construction is often far flimsier than that used on the floor of the trailer, and it is subject to some of the worst abuse as horses clamber up and down (and leap, and plunge, and scramble, and otherwise try to avoid being loaded).  A ramp that gives way as a horse steps on it can be a lifelong confidence-breaker, so make sure it can support his weight, and that it is equipped with some sort of anti-slip material, whether it be treads, rice mats, or rubber.

    Hitch up your trailer to your towing rig.  Make sure that rust hasn't caused your hitch to seize – a can of WD-40 can do wonders here.  Look carefully at all the hitch components, as well as your safety chains, examining them for tiny fissures that could indicate metal fatigue.  The risk of this is greater if you drive on very rough roads or those that are salted when icy. 

    Hook up your electrical system and have a friend stand behind your trailer to confirm that the lights are working as you try your brakes and turn signals. 

    Back the trailer up onto a block so you can check the bearings.  You also can jack the trailer up for this to free up each wheel in turn.  Spin each tire with your hand, and listen carefully.  Rolling or grinding noises, or any harsh, thumping sound, indicates that your bearings have had it.  Grab each tire and try to move it from side to side, or in and out, too – any play means the bearings are loose or worn.

Your mechanic can do a more thorough inspection, including an assessment of your trailer's brakes.  A complete, yearly going-over is a good idea and should include removal of your trailer tires to lubricate the bearings, and a thorough check of your wiring and lights.