tab_dim (t, tab_natural_dimensions, NULL, NULL);
tab_vline (t, TAL_GAP, 1, 0, split_cnt);
tab_vline (t, TAL_GAP, 2, 0, split_cnt);
tab_dim (t, tab_natural_dimensions, NULL, NULL);
tab_vline (t, TAL_GAP, 1, 0, split_cnt);
tab_vline (t, TAL_GAP, 2, 0, split_cnt);