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.

Lowrance
GD001 (1/4-20 Male Thread)	GlobalMap - 2400, 3000, 3200, 3300C, 3500C, 3600 iGPS, 4000M, 4800M, 4900M, 5000C, 5500C, 6000C, 6500C, 6600C HD, 7000C, Baja, Baja 480C  |  LCX -15CI, 15CT, 15MT, 16CI, 17M, 18C, 19C, 20C, 25C, 26C HD, 27C, 28C HD, 37C,  38C HD  |  LMS - 240, 320, 330C, 332C, 334C iGPS, 335C DF, 337C DF, 339C DF iGPS, 480M, 480MDF, 520C, 522C iGPS, 525C DF, 527C DF iGPS   |  X100C  |  X102C X105C DF  |  X107C DF  |  X125  |  X126DF  |  X135  |  X136DF  |  X47EX  |  X510C  |  X515C DF  |  X71  |  X86 DS  |  X87  |  X88DF  |  X91  |  X96  |  X97  |  X98DF
GD003 (11/16-16 Male Thread)	GlobalMap 1600  |   GlobalNav 310  |  LCG-2400  |  LMS-150  |  LMS-150GPS  |  LMS-160 MAP  |  X22A  |  X23  |  X24  |  X25A  |  X25B  |  X28  |  X29  |  X38X45  |  X48  |  X49  |  X51  |  X52  |  X58DF  |  X59DF  |  X65  |  X75  |  X85
GD015 (1/4-20 Male Thread)	LCX-104C  |  LCX-110C  |  LCX111C