Garrett Ace 350 Owner's Manual page 19

SENSITIVITY Pushbutton

Use the (+) or (-) SENSITIVITY buttons to step through the
eight (8) sensitivity levels, which are continuously shown on
the LCD screen.
Use higher sensitivity levels when searching for very
small or very deep targets. Use lower sensitivity levels in
locations where the detector is behaving erratically due to
excessive metallic trash, highly mineralized soils, saltwater
beaches, electrical interference or the presence of other
metal detectors.
18 Garrett Metal Detectors