Horizontal rules are used to separate the title from the column heads, the column heads from the entries, and the entries from the notes. There are only three places in tables where full table-width rules should be consistently used: below the table title, below the column heads, and below the last row of entries.
If a table contains vertical rules, delete them from the manuscript copy that you submit to composition when requesting it to be set. Also, eliminate horizontal rules that appear in areas of the table other than those described above. Insert a row of white space instead, as space and length of the table permit, to make the table easier to read. Only use rules within the table if the entries are text heavy or otherwise need clear delineation. Even if a table was published with lots of rules in a previous edition, those rules should be deleted. Additionally, column heads as well as table entries may require straddle rules when data applies to more than one column and/or row of the table.