If the line markings on your synthetic surface are wavy it can be for 2 reasons: If they are sprayed onto the surface then it is due to the quality of your application. In most cases painted lines will fade away over time, at which point they can be re-marked professionally. If you can't wait that long then another alternative is to spray over the existing lines with a green paint before overmarking the new lines. Technical Surfaces offers a line marking service and unlike waterbased paints our special 2 part line marking compounds can last in excess of 12 months. If, on the other hand, you have inlaid lines on your surface, wavy lines might suggest more problematic issues. If we assume the lines weren't wavy after installation then the most common cause is movement in the surface carpet. Most surfaces are 'dynamic' meaning they are simply held in position by the weight of the infill (approx. 150 tonnes on a sandfilled surface). Even given this sheer weight, in certain circumstances the surface can creep sometimes uniformally and it is this movement which causes distortion of the lines. Special equipment can be used to help rectify this but ultimately it may be necessary to cut out sections of carpet and insert new lines. Technical Surfaces would be happy to offer futher advice on this issue.