How To Play Two or More Down Bows
Occasionally you will see two or more Down bows marked. It will look like this:
What the composer is telling you to do is to play the first note and then lift the bow off the string and circle back around to the frog. Once you reach the frog make sure the bow has fully touched the string and is not bouncing before playing the next Down bow.
This is often used in an orchestra setting where the composer wants to have a dramatic effect with multiple Down bows at once.