End plates simply close off the two ends of a trench drain to keep concrete out of the channel drain. To save the contractor time we believe in attaching these at the factory when possible. When this can be done the end plate is sealed water tight and won't slip off of the drain during the pour.
We do offer an end plate for field attachment. This is used when the length of the drain is not known at the time of manufacture. Simply put the end plate on the end of the trench with some sealant or screws and cut the top to the required height.