I had my neighbor who owns a truck repair shop said he sent 2 mechanics to meridian MS to adjust brakes on a big rig. said the driver said the d.o.t. would not let the driver adjust the brakes unless he was certified to do so & had certification with him. I forgot why he told me the driver or co called him to go out being he was over 200 miles away on the AL/TN line. I have heard of scales in some places not letting drivers or o/o adjust anything unless certified. any one else know of this. I am not certified, but I adjust my own brakes if ,when neccessary. I have no certification on electrical components either, but I do change my own headlights, marker lights, e.t.c. kinda makes me wonder. if you travel on i-24 thru tn you run into mt eagle. the last time I went thru there was years ago, but remember that there was a pull off just befor the downgrade & big signs saying drivers pull over & adjust brakes before going down hill, or something to that affect. how could that be if you have to be certified? or is it law in some states & not others?

396.25 explains the qualifications.