Any excess material that is leftover after the grate has been put in place can be trimmed but it is certainly not required. In fact, there are a couple of reasons that leaving the extra material is beneficial. It can act as a “pre-filter” and remove some pollutants from the stormwater before they have a chance to get below the grate and into the Ultra-Drain Guard. Also, if there is a possibility that the Ultra-Drain Guard will be reused in the future, the excess material will make it much easier to be reinstalled.
If trimming of the material is necessary/desired, this can be easily done with heavy-duty scissors or a utility knife.