Landscape Timber 4 foot long x 8 inch high black. This border timber may be used for containment or perimeter border in landscaping or on the playground. In some installations, playground surfacing may be less that 12" depth within a border system at 12" high. Higher border timbers may create a trip hazard. Consult CPSC Publication 325 for information on types of surfacing and recommended (or required) depth.