sentences:  There is role of materials used to make the ropes of net (such as an iron rod grid will not work as good as flexible and extensible ropes), and the tension or stretch used to make the net (stored in the ropes), also have some roles.The net is to be set at an appropriate height from the hard ground, so that the object, along with the rope, does not clash with the hard ground.The mesh hole size should-not be so big that falling object/people/part of it could pass through the holes.