The DSA test gives you a qualification to allow you on the roads alone, to learn to drive an LGV.
No one can teach blind side reversing until you have got the hang of how a vehicle turns, the pivot points were mentioned, good advice, but too early in the learning curve. Curtainsider tensioners & buckles? In 30 years I doubt if I have come across even half of them.
Let’s drop a trailer.
Remember not every trailer has air suspension, not every tractor has it either, some will have run up ramps, some will be deep pin trailers, some may have sliders. You are never going to get through all that and understand it in a 7 hour classroom session.
Find somewhere level, preferably dry, because you are going to get out of the cab into a muddy puddle otherwise. If it is in a line of other trailers, try to keep it straight, otherwise when you get home on Saturday morning you will find there is no room to park up because some ■■■■ has parked a trailer cross-hoppled.
Let’s drop a trailer.
You have just passed your driving test and done the required couple and uncouple exercises, using the handbrake. Well done, now forget that.
Let’s drop a trailer.
You are happy where you are parked, the trailer is level, the marker lines are visible at both sides equally.
Put on the tractor handbrake and climb out of the cab backwards. Can you remember which side your cat walk steps are?, good, walk the opposite way round, stop go back, shut the drivers door! (lock it, if in Glasgow, Poland or Liverpool)
Does it look good? then retrieve your number plate, (lights bulbs etc. If necessary) (see above) Walk past the trailer handbrake and put it on, it may be a ratchet, it may be a button, it may be a winding handle. Stow the number plate away and climb onto the catwalk, release and stow away the suzies and cables. Climb off the catwalk backwards and either open the door and raise the air suspension slightly or wind the landing legs down using both gears. You are trying to keep the trailer height roughly the same as it is when the trailer is at normal ride height, modern trailers bend at the neck, they are meant to. Depending on the company you work for dictates how many turns of the winding gear you give it 
. I just want the legs to support the extra weight of the trailer and load when I eventually drive from under it.
Now go back to the drivers side of the lorry, remove the 5th wheel clip or retainer and release the jaws. Now you can climb back into the cab. You can then slide forward an inch or two as you lower the tractor air suspension (If used or fitted). This allows free access & ingress without ripping off the mudflaps or covering them in grease. Drive out slowly and check trailer is not sinking or tipping up if loaded nose heavy.
This is a very tongue in cheek method and took me almost seven hours to choreograph it, hopefully it will take you less than two minutes to do it in the real world.
Well done you have dropped a trailer.
For deep pinned trailers, either lose some weight, or find an article on split coupling and which companies allow it, some do, some don’t and the only way you will find out is when you get a bollocking off a brown 18 year old guy who struggles with English
Most look completely bewildered when the machine asks for the mileage (shock, horror!) AND the vehicle registration. 
