Slick steel cylinders and spiked blooms of barbed wire sit atop imposing 30-foot-high rectangles of metal and concrete. Eight of these structures are lined up side by side along part of the U.S.-Mexico border, commissioned mock-ups specifically designed and waiting to be tested for their durability and strength. For the next 30 to 60 days, a cadre of military officers, border agents, and engineers will try to scale, dig under, or break each of these border wall prototypes. Simple, arresting photography works to underscore the very nature of this venture.  WFM