Many moons ago I was helping demolish a stud wall with brick in-fill. I found a manky old cotton-bound wire poking up through the floor. "Nah, don't worry, it won't be live", said the bloke in charge of the works. It was. Tres tingly. I learnt never to trust a joiner when it comes to electrical stuff.
I guess you're using joiner in the wood sense. I got chatting to an electrical joiner working on a pavement joint outside a neighbours the other day. He was telling me how they join the live cables without disconnecting the supply to the whole street. Basically the answer was 'carefully'.
Many moons ago I was helping demolish a stud wall with brick in-fill. I found a manky old cotton-bound wire poking up through the floor. "Nah, don't worry, it won't be live", said the bloke in charge of the works. It was. Tres tingly. I learnt never to trust a joiner when it comes to electrical stuff.