... as common as broken, but a slight deformation of the car and pedestrians has a certain security. 2. Anti- ... mouth of the Manhole set to U-shaped, with a T-type synthetic rubber, U-shaped slot embedded in ... slip: 3mm tread covers convex surface, and thus play a good non-slip effect. 4. Anti-impact: Manhole ... with the colossal surface, directly on the T-rubber, and dealt with gently, to eliminate noise.