A boxed cluster (a row or column) is called a group box or an area. An area provides a visual cue to users by isolating and naming controls that work together. The area can contain as many tiles, rows, and columns (unboxed) as necessary. The label of an area should indicate its purpose.
If controls relate to each other, put them in an area. The Base Point cluster in the Block Definition sample dialog box demonstrates this technique with an area formed from a cluster with a label and a border:
However, do not overuse areas. White space is also an effective way to group tiles. Do not put a box around a list box; this looks too busy.