How St Andrews Foursomes works:

You must choose prior to play, which one of your team takes the SECOND shot as opposed to the first. Both players tee off and you can choose from either drive, unlike regular foursomes. But you must nominate a player to take the second shot from your chosen drive.

This will be scored in stableford points and using the regular handicapping formula for foursomes which is 50% of the combined handicap.