Pin Attributes describe the appearance of a data field in vvvv.

Most important is if it is an input or output.

[Input("Input", DefaultValue = 1.0)]
        ISpread<double> FInput;
 
        [Output("Output")]
        ISpread<double> FOutput;

In between the () brackets a comma seperated list of pin attributes can be set like that:
PinAttribute = PinValue,

The value you specify has to be of the pin attributes' type.

All available properties are listed under: pluginspecs/html/AllMembers_T_VVVV_PluginInterfaces_V2_PinAttribute.htm

examples:

Specify a default value for a pin. This is also the value used on ALT+rightclick (reset pin to default).

DefaultValue = 255.0

Specify a not spreadable pin. The pin has only one slice and the user can't change that.

IsSingle = true

Specify the pins visibilty.

Visibility = PinVisibility.Hidden

Speficy a pin to be of type filename to show file-dialog on rightclick.

StringType = StringType.Filename

Creates a dynamic pingroup, where the user can specify the pin count via Inspektor. This will only work in combination with a ISpread<ISpread<T>> with any T.

[Input("Input", IsPinGroup = true)]
        ISpread<ISpread<double>> FInput;