Found some metal "J" channel edging at Home Depot...it's gonna be my drip guard/gutter that will capture any water that gits in between the hatch and the sides and channel it to the backside.
Of course...it rained today before I found it and of course...the bed got all wet. At least I knew ahead of time that the hatch wasn't water-tight so there wasn't anything in the bed at the time.
I just need to trim the rest of the Coroplast that's hanging over the edge and then secure the "J" channel in place. It will slide in between the 2x3 wood and the Coroplast. I love it when a plan comes together....
http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053