Border formats defined in a pages file apply to page borders only. Border format names should end in Border as a convention. The default border format is no border at all. The properties you can specify are the same as those available for border formats you can define in the formats file; see §8.2 Defining border format components.
To specify properties for page borders:
[LightBorder] type = single color = black thick = 1pt space = 6pt
[HeavyBorder] based = LightBorder thick = 2pt
[DoubleBorder] based = LightBorder type = double