Box/Block and Client Rectangles

Hello dear W3C community,

Could you give a definition for the client rectangle please?
As I understand, DIV element has 1 client rectangle; TABLE (both
block-level and inline-level) has at most 2 client rectangles: for the
caption box and the table box; IMAGE has 1 client rectangle.
Range can have several client rectangles based on the selection.

Another question is regarding the inline boxes/blocks which span across
several lines. There is no API to get borders (width, height... for all 4
segments) of the corresponding client rectangles which are also boxes, only
of the corresponding inline box/block which is an element in the DOM tree.
Should I expect that spanned inline-level element always looks like this:
_________
|_/_/_/_/_/_
_________
_/_/_/_/_/_
_________
_/_/_/_/_/_|

Where "_", "|" are borders, "/" is the content.

Thanks.

--
The best regards
  Ruslan Fayzrakhmanov