The invention relates to a grid of synthetic material with two groups of parallel, load-bearing strands, wherein the strands of the first group extend in the longitudinal direction of the grid and the strands of the second group extend transversely to the longitudinal direction of the grid and the strands of both groups are joined together at their points of intersection. Alternating first and second portions are formed with strands extending in the direction of one of the two groups. The strand spacing of the first portions are larger than the strand spacing of the second portions. The second portions can be of an increased strength and can be used to fasten the grid without aids.