Raymarine RAY91 VHF Installation And Operation Instruction Manual page 46

2. Drill the mounting holes using a suitable size drill bit.
3. If required, use a 6.5 mm (0.26 in) drill bit to drill a hole for the holster's power cable.
4. Hold the holster in place and secure using the screws provided.
5. Place the Handset into the holster, ensuring it clicks into position.
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