Funny when Im leaving building sites, noone ever bothers to check inside my tank to check that Im not nicking any mortar! 
Think I’ve mentioned before, we get stopped at security at MCP Oldham for more than one copy of the tabloids printed there, all 'cos of one numpty selling bundles of em at a carboot, frequented by his line manager.
I’ve done min wage security and it’s crap work, but I sympathise with the guys doing it cos when owt goes missing, the resulting s**t comes all the way down the pecking order (from the client and the security firm) and stops with them.
if they have a sign saying something along the lines of “all vehicles entering or leaving this site are subject to search” i do not have a problem with it. no one should.
Like it has been mentioned before you drive a truck, its your job, the security guy has been told to search wagons, its his job. let everyone get on with thier job and you will have a lot less stress in your life. in my opinion the ones that get angry about it have something to hide.
if i have been on guard duty with the navy and then someone gets funny about us searching them, either on the way in or out, we just drag it out a lot longer. they cant complain bacause we are just doing our job. get it over and done with, with the minimum of hassle and you will be on your way in no time. if you make a fuss you could be there a good ten minutes. ive had one lorry driver with a curtainside 40ft having a mank and a moan about it on the way in. he wasnt happy with us when we made him open both sides of the curtains up and then again on the way out. if he had been ok and just let us do it we would have just looked in the back! (sorry if it was you but we did have a job to do) 
I think some of you may have misunderstood the original question.
The reason that we are asked to open the back is to make sure we haven’t stolen anything, THAT is my problem, all I’ve done is my job, delivered a load of whatever to wherever, during my time on site I exibit no signs of stealing anything, it may be the 1st time I’ve been to the place so I wouldn’t know anybody ‘on the inside’ yet I still have to prove my innocence, yes I know that there is a disclaimer on entry to most places but from my point of view all this procedure does is label us as 2nd class citizens & that is plain wrong.
I have no problem with the security guards as they are just doing their job, it’s the jumped up holier than thou tossers who make the rules that get on my man ■■■■■, if it was a random process then it would be fine but it isn’t 
newmercman:
I think some of you may have misunderstood the original question.The reason that we are asked to open the back is to make sure we haven’t stolen anything, THAT is my problem
And that is not necessarily a bad thing, if they have a current issue then your above suspicion, I agree it’s a pain in the rear, but one which they believe is required to help prevent shrinkage.
Oh and btw no-one can force you to be searched (car,body,bag,trailer etc) if they have suspicion that your in possesion of stolen items they can detain you and call the police and have them search you. A numpty ‘store detective’ supposedly SIA licensed at Wooly’s found this out the hard way and ended up with a broken wrist the sack and ordered to pay me compensation. 
I delivered to B&Q RDC at Doncaster recently,and on the way out,a fat miserable ■■■■■ “ordered” me to open my back doors,really got my hackles raised 
I was empty,apart from some crappy,irregular sized pallets,shrink wrap and banding,left over from a previous handball delivery.
“What’s that ?” she barks…for a few seconds,I deliberated over a whole selection box of withering sarcastic replies
However,as we deliver there regularly,I was forced to adopt a polite common sense attitiude,and be Mr Reasonable itself 
But never in the history of road haulage has a security guard deserved a smack in the moosh as much as she did 