Been asked to give a quote on a landscaping job that includes some hardscape. Customer wants a 65 linear foot "fence" on a slight grade that increases from left to right at a total slope increase of 3.5 feet. When I asked him if he wanted a white vinyl picket fence he said he wanted that "block stuff". Looked a versa-lok but would like some input from you guys that have experience with retaining walls. What would you recommend? Other than the obvious improper installation, what are some major reason's for wall failure? Thanks!