There are many ornamental and structural applications for columns including lamp posts, mail boxes, entry columns, wall stabilization, landscape accents, and more. The key is to keep each course level (may require shimming) and all four corners vertically plumb. Interlocking columns and walls together will add stability to both. Spacing of the columns is usually determined by the overall wall height. In general, for walls 3 feet high or less, spacing the columns 8 to 10 feet apart is adequate.