The Dovetail Column Lock is a one-piece sacrificial form designed to lock the base of a column into the interior of a slab. The contractor places the plastic form on the slab footing prior to placement of the adjacent slab on grade so that column reinforcement is centered within the column lock. With the column form over the opening, the fresh concrete fills in the space belowgrade during the column pour. The effect of the concrete’s placement belowgrade provides the column greater lateral resistance to horizontal pressures, such as wind. Coastal Columns. 409-939-2748.