What is this key for?

[Tel]

On the Apple USB keyboard, ISO layout (standard UK), above the 7 on the number pad, looks like a rectangle with an X trough it. I've never seen them on any other keyboard and have no idea what its for. Make a nice bleep everytime I press it but surely that can't be its only use

 

[Laser47]

It means Clear,

From the Guides Section
http://guides.macrumors.com/Keyboard_shortcuts

 

[mpw]

Apple really should make their keys more obvious. The other day I went into the only local 'Authorized Apple Reseller' with a query I hadn't been able to figure out myself on the off-chance they may be able to help. Unfortunately the Manager/owner wasn't sure which was the option key to reset the PRAM.

 

[kungfu]

Apple really should make their keys more obvious. The other day I went into the only local 'Authorized Apple Reseller' with a query I hadn't been able to figure out myself on the off-chance they may be able to help. Unfortunately the Manager/owner wasn't sure which was the option key to reset the PRAM.

I think it's cmd-opt-p-r... just in case you still needed it.

and the clear button works just like the clear button on a calculator... at least, that's how I use it.