In 'Scales in One Position' it is vital to have a free movement of the left elbow. This is so that the left hand stays at the same angle over each string.
Pluck with the 4th finger across all strings making sure you lead with the left elbow.
Try this exercise without a shoulder rest, with the violin resting on your collarbone. Check that the left arm can move freely, and that you are not raising your left shoulder....
