The boxhead refers to the area of the table containing the stub heads, column headers and spanners. You can control how the boxhead is displayed when the table is printed using the Format Print (Table) dialog. To bring up this dialog, choose Format Print (Table) from the Edit menu or right-click anywhere on the table and choose Format Print (Table).
The boxhead setting is found in the "Layout" section of the dialog. It only has meaning for a table that spans many pages and it only has an effect in the print preview and, of course, the printed table.

The options are:
No boxheads – Only the table title is printed on each page.
Top of table only - Table title and box head only appear on the first page of table.
Top of each page – Table title and box head appear on each page of the table.
Use the Format Print (Table) dialog to set the boxhead frequency for a single table. Use Preferences and Default Formats to set the default boxhead frequency for all tables in the file.