If lock to the baseline grid is enabled, Fred4 adjusts the amount of the white space between outer box and inner objects, and also makes sure that the top of all inner objects starts on the baseline grid. Warning: a necessary condition for that to happen is that the margin value is divisible by the baseline grid. Therefore, if the baseline grid is, for example, 10pt, while a user requested boxing with 6pt margin, the margin is automatically increased to the closest baseline grid value, e.g. 10pt (should the user specify 12pt, it will be downsized to 10pt).

The following screenshot shows the difference between boxing with the baseline grid lock enabled (left) and disabled (right). Please notice that title frame and body frames on the left article start on the grid, while they're not aligned in the right article.