Bind visibility property to a variable

I have a Border with Label inside a Window,

<Border x:Name="Border1" BorderBrush="Black" BorderThickness="1" HorizontalAlignment="Left" Height="21" Margin="229,164,0,0" VerticalAlignment="Top" Width="90" Opacity="0.5">
    <Grid>
        <Label Content="test"/>
    </Grid>
</Border>

I have also a Variable:

public bool vis = false;

How could I bind the vis variable with border Visibility property?