This command is used to specify the place from which the left edges of a table are measured, when the table is nested within a block or another table.

Normally a nested table’s edges are measured from the inside of the parent cell’s rules after also taking into account any cell padding. Searching back through the hierarchy of parent tables and blocks, if one is found with more than a single column, or one had its number of columns specified explicitly, then setting <?tbabsleft=1 will measure the table from the border of that parent’s column edge. This will still be inside any rules of the parent cell but will ignore any of its cell padding. If no conforming parent table/block exists then <?tbabsleft=1> or <?tbabsright=1> will measure directly from the frame column boundary. From these left and right boundaries, the current table margins will then be applied, along with table rules and padding etc., in the normal way.