What are these symbols?

[Zero999]

well it sounds like a cordless drill is not a good option when you suspect wires are in the wall.

You shouldn't use any drill if you suspect live wires in the wall. The safest thing to do is turn of the power and use a non-contact voltage detector just to make sure.

[Mechatrommer]

earthing mechanism is just one attempt in safety. but it will not keep you 100% safe, the other (major) factor, is human intelligence. i second RayJones. my 2cnts.

All the same scenario using devices that are not mains powered. You can only protect against certain forms of stupidity.

[Simon]

well it sounds like a cordless drill is not a good option when you suspect wires are in the wall.

You shouldn't use any drill if you suspect live wires in the wall. The safest thing to do is turn of the power and use a non-contact voltage detector just to make sure.

Power tools are sold all over the world, ever tried picking up a wire through solid rock ? in some countries walls are 2+ feet thick, you don't always know what is in there. If the earth does fail the RCD will protect you, after all if we go on the assumtion your doing it right and using a wire detector and doing it properly you'd also not be working without an RCD. Portable RCD's are also available. I use one on my saw

[Zero999]

Power tools are sold all over the world, ever tried picking up a wire through solid rock ?

Yes, it's possible with the gagit linked below.
http://www.google.co.uk/products/catalog?client=opera&rls=en&q=non-contact+voltage+detector&oe=utf-8&channel=suggest&um=1&ie=UTF-8&cid=1052363795548288751&sa=X&ei=jBhqTcTQNceLhQfom9mhDw&ved=0CDUQ8wIwAA#

in some countries walls are 2+ feet thick, you don't always know what is in there.

What difference does that make? You won't be able to find a drill bit that long which will fit into an ordinary hand drill.

If the earth does fail the RCD will protect you

No it doesn't, if the wires in the wall are not protected by an RCD, it makes no difference whether your drill has RCD protection or not, if the earth fails and you hit a cable, the drill's case becomes live.

[Simon]

I have a dril 2 ft long  it's a N10 for putting wires through walls, yes in the case of the drill a portable RCD won't protect. However it will protect the chainsaw. ike I said, there are different methods of protection and one only needs to be followed