Hello there,
from the Warwick Bass Manual, page 6:
"The Just-A-Nut II
All current Warwick basses come with the Wilferite Just-A-Nut II. The nut is fully adjustable for easy
playing in the first position. The Just-A-Nut II (somposite) represents a major improvement in engineering over the Just-A-Nut I (brass). This new
design allows you to make string height adjustments at the nut without taking the strings off. The two allen screws that are inset
on the top of the nut allow you to easily change the nut height. By turning the screws clockwise, you raise the nut. Turning the
screws counterclockwise will lower the nut. Now you can experiment with different string gauges without having to go through
the hassle or expense of shimming or filing your nut."
Note: Please loosen the strings before adjustment!