Permanent Mulch Recycled Rubber Border - 10 Feet Long x 4.5 Inches Wide | Weed Deterrent | Easy Install | Scatter-Proof | Landscaping | Paths | Eco-Friendly Design

Not sure of any protective end caps, but They make a rubber mulch like roll that is meant to go under fences and eliminate trimming. https://a.co/d/0hXoEd2U (Personally I don’t like this style of aluminum fencing for this very reason. The drop-rail where the bottom rail is flush and no pickets poke beneath is SO much easier to trim around and saves on trimmer line. Obviously it is too late now, as your fence is already installed, but figured I’d post it anyways for anyone considering getting an aluminum fence)