Perimeter Walls

Perimeter Walls acts like Reinforced Concrete, it can be only in the Ground layer, it appears in Moderate+ prison (Shankton State Pen, Jungle Compound, San Pancho and HMP-Irongate) Tower Guards also seen surrounded with perimeter wall. You cannot chip the wall, you can go past it by using the Grappling Hook in the Roof layer or dig under it.