This switch has two different purposes on MotorGuide Foot Pedals depending on your model. 

On 12 Volt or 24 Volt Motors, It controls the Momentary, Continuous, High Bypass Selection. 
On 12/24 Volt Motors, it controls the 12 Volt, OFF, 24 Volt Selection.

(Will not fit Tour Series, X3 or X5 Models)

Part Number: 8M3003621