If you are taking about then neck of the shower head this is what you must do. its no need to turn the water off to the house or to the bathroom first you will need a pair of channel locks and some Teflon tape. first remove the shower head if you dont want to scar the nut on the shower head place cloth between the pliers and the fitting, once removed (very important) turn the channel locks upside down stick one side of the blue handle up in the neck of the shower and rotate to your left to loosen if you are having a leak leak there it should already be semi loose, once removed wrap the threads with the Teflon tape and re-insert making sure it is tight, then wrap the the outer end of the neck with Teflon tape and place the head back on.The reason it leaked is because the plumber who installed it did not tighten it up completly because he wanted it to look straight coming out of the wall and the additional water pressure causes it to leak wheras the hot water causes it to expand and seal