In a complex page layout with several columns, it is often preferable to separate columns vertically with a fine rule. Similarly, many letterheads require a quite heavy horizontal rule below the company name, or above the address details at the foot.

If you have worked through the Designer Exercises, you will have added several rules to a typical master page. They were used to separate the header and footer, and also to add a ‘fold mark’ to the left edge of the paper as a coloured hairline.

Properties

Colour ... (from nl‘colours)
Style ... one of Solid, Dash, Dot, Dot-Dash
Weight ... line weight in points

If you want to enclose a rectangle, it is much more efficient to use the ‘Box’ which has some additional properties such as background shading.