How does the Schaller fine-tuner (the tailpiece with the additional screws) work?
When stringing the guitar, please tune it as usual using the machine heads. Loosen the screws on the fine-tuner to the half-way point (or to the 3/4 point). When the guitar has been tuned using the machine heads, they can be more finely adjusted as follows: Tightening the screw raises the pitch; loosening it lowers the pitch.
When making the initial adjustment, please allow the screws to protrude a little more than necessary (but not far enough to allow them fall out). This means they can be tightened accordingly during playing.
If this tightening results in the screws being tightened to the limit, please loosen them again and re-tune the string using the machine heads as usual. Then fine-tune again by tightening the screws once this has been done.