What is a "star drive lag" ??

The star refers to the shape of the bit that fits the fastener. Just
as there's hex, square etc. Go to: http://www.grkfasteners.com
there's a ton of different types there.

FWIW -- star drive screws are expensive....almost scary in fact. But
-- once you can pull board together one handed with a a 1/2" drill with
no cam out of the bit, you'll understand. Any more, all exterior
construction get these screws. You'll have to find a lumber yard or
contractors source house to buy them.

Good luck,

DAC