Nokia 6600: lock keypad, unlock keypad

howdi fellow Nokiers,

can someone please remind me (it isn't all that obvious from just playing,
and i lost
the manual and CD) how to lock the screen (and also how to unlock it)?

also, once i know how to do that, how can i assign a quick handle to it?
like put it in goto,
or even assign one of default buttons (either left or right).

muchas gracias
cheers, gil