flagstone flooring interlocking pavers paving block FLAGSTONE FLOORING Edge restraints are a critical element to the durability of flagstone flooring installation. They prevent the flagstone from moving and shifting over time. Unilock® offers several options for restraint. Unilock’s own plastic Edge Restraint is both economical and effective. Various concrete edging materials also work well with the added benefit of complementing the flagstone flooring with color and texture.