Tensioning locks with key guides

[PickPick]

I don't know if key guide is the correct expression, but what I mean can be seen in this picture:
http://tinypic.com/e3wus
There's some sort of slot cut into the front of the cylinder.

So when I encounter such a lock I like to apply tension by using a metal strip that fits snuggly into this slot.
http://tinypic.com/e3wwl
This way the keyway stays completely unobstructed and your tension tool is practically a part of the core, therefore you get very direct feedback and tension control. For tension tools I use old picks cut off at various heights and sometimes the straight part of a tension wrench.

[drv]

Aaaaah, the Vachette lock.

Yes, ideal how they made this slot all over the keyway
I always use it to hook my wrench into as well.

But they are often quite a challenge to pick ...