Abstract: A foul or base line segment of plastic or rubberized material suitable for installation in various fields of athletic activities comprising: a generally horizontally extending lower flange for installation in a field beneath ground or playing level; a generally horizontally extending upper flange which upon installation will be clearly visible at ground or playing level to demarcate fair and foul zones or areas, for example; an intermediate web extending generally vertically between the lower and the upper flanges and having a lower edge integral with the lower flange at about the transverse midsection of the lower flange, an upper edge integral with the upper flange at about the transverse midsection of the upper flange, and a retaining element formed in at least one end of the web; and a coupling member cooperating with the retaining element to couple the one end of the web to an end of a like foul or base line segment placed end-to-end with the foul or base line segment to extend it and to ensure installat