A box can be used to apply a border and/or a color fill to one or more contiguous paragraphs, tables, or images.

A box starts when a mapping sets the Start box property and ends when a (possibly different) mapping sets the End box property.

The appearance of the box is determined by the box style that is in effect when it starts.

One of the properties of the box style is whether the content within the box is breakable. If the Breakable box property is not set an implicit bind is applied to the box content.

TopLeaf does not support general nesting of boxes. The only nesting allowed for boxes is that a box whose style has the breakable property set can contain a box that is not breakable. See also Limitations - Box processing.