A sheet mesh of plastics material for application to roof guttering to prevent the entry of unwanted materials into the guttering. In use the mesh is affixed along one edge to the roof and along the opposite edge (46) to the top outside edge of the guttering. The mesh comprises a first array of parallel strands (42) aligned in a first direction integrally moulded with a second array of parallel strands (44) aligned substantially at right angles to the first array. The strands (44) in the second array are made from a stiffer material than that from which the strands in the first array (42) are made. The mesh is preferably manufactured as a co-extrusion of LDPE-rich and HDPE-rich materials.