I have a customer who has lava rock already in place but no border so you can imagine how fun that is when im trimming. I need to put some sort of edging in to keep the rock in the beds. The yard is on a slope and is very uneven and stone or block are out of the question. What type of border would you reccomend? I was thinkin about the metal edging but have never used it. I need something that is low profile but works good and looks good, not anything like that plastic crap!