Lock down tool box - How?

I have one of the chest-type toolboxes for my truck (hold over from a previous truck) but it has never been installed. How do most of you attach them to the pu box so that they don't slide around or to keep them from being stolen?

I was thinking about screwing a couple of 2x4's to the bed, and then screwing the toolbox to the 2x4. Any ideas or comments?

Thanks all,

--->Rob

my boss has one in the bed of his 2002 silverado. its bolted to the floor of the bed