I would also add as I believe is shown in the Premier Guitar video I first posted, as the safest rule of thumb, VERIFY presence of current, Discharge like they show with wire and resistor,,,have hand in pocket, plus always verify with meter that the caps are fully discharged. I once was working on a bathroom and had to deal with 2 electric circuits, one was 110 the other 220. I didn't have a tester to verify the breakers I switched off actually killed both circuits. Later after most of my work was done, I discovered the 220 was hot the whole time and I could have easily been zapped had I been unfortunate enough. After this, I now have the proper testers and VERIFY no current before working around house wiring etc.