Instructions:
(a) Remove one factory knob from either side of unit.
(b) Turn key clockwise and remove from lock.
(c) Screw GPS/Sounder lock into female thread until tight.
(d) Insert key and turn counter clockwise.
(e) Knob will spin freely when locked correctly making it impossible to remove..
Note: Lubricate often and record key number for replacement keys when lost.

Humminbird
GD001 (1/4-20 Male Thread)	NEW 2005 – All 900 Series
GD004 (1/4-20 Female Thread)	Legend - 1000, 1000 Deep, 2000, 2000 Deep, 3000, 3000 Deep
GD019 (1/4-20 Female Thread)	Matrix97