The Celtic tattoo design is multi-faceted. It can be in the form of a cross. It can also be in the design of a knot. These knots can be round, triangular, square or just about any other shape desired. But what makes it a Celtic design? All Celtic knot designs can be inked to fit into a particular shape as well. Many times you will see a stone cross, tombstone, doorway or other marker with the Celtic knot design drawn inside the boundaries of it's perimeter. The integrity of the knot design still holds - It will be one continuous line from the start to finish.