Stowe Wind Instrument

[Guest]

I have a Stowe System with two instruments, a Navigator 2 and a wind direction. The navigator gives the wind speed, log, distance etc. The wind instrument gives wind direction only.
Question How do I adjust for Zero on the wind instrument. It has a movable bar on the back that may be rotated

 

[Guest]

This is the model with a black "barrel" at the rear of the display? The manual for mine says:
"When convenient, e.g. motoring directly into wind, small adjustments can be made to "zero" the wind angle pointer. This is achieved by slackening the 2 adjustment lever screws on the rear of the display head, half turn only, and moving the lever in the direction the pointer must be moved. Re-tighten the screws carefully but DO NOT overtighten."
The adjustment lever on mine has a double-headed arrow labelled "Zero" next to it.

 

[Guest]

Alan, Many thanks for your help