On our 2002 E450, cover is rectangular, long edge parallel to bumper. It's hinged on the outboard (driver fender) end. On the INBOARD end, there' a little catch on each side of the long edges, right where they meet the short inboard end. Easy one to feel is between the brake fluid reservoir on the master cylinder, and the coolant reservoir tank. Opposite that, on the forward edge of the cover, is a matching catch. They only need to be pulled outward at the bottom edges to let go of the box and allow you to lift the cover. Then you can un-hinge it on the outboard end. Should be a legend inside of what's what.