Sweeee-eeeet! If you clamp a piece of wood across the whole front of the shelf just below the shelf above the batt, it will kind of be like a big foil or waxed paper box. You can roll the edge of the batt up over the wood and through the space to hang down a little. Tape a tape measure to the one side of the shelving unit down to the floor. You can them pull down how much you need by the tape measure and trim it off up at the wood for a nice straight edge.