The scarf hold position may be used whilst ground-fighting.
This position is good to control your opponent but does not have many submissions readily available. There are lots of escapes from the scarf hold so don't stay there for too long.
Sit next to your opponent with your back against the side of their chest.
Take your right arm and place it round the back of your opponents neck. Grab hold of either your gi or theirs to prevent them pulling their neck out.
Take their right arm under your left arm-pit and pin it there with your left arm. Grab hold of the back of their right arm as shown. This is the strongest grip to use to prevent your opponent from pulling their arm out.