The most recommended materials are HDPE plastic and the specific mention of using an “opaque material” as a method of fencing (Figure 1 ). Technically, insertion rubber and concrete walls can be considered as an opaque material and therefore, that would make this the most commonly recommended material and method of fencing in these guidelines. The use of transparent materials and thinner plastic were the most commonly recommended options pre-2015, with only TMR suggesting the use of insertion rubber as a fencing material (Table 4 ).