Nor could they be tunnelled under easily, as the bottom segment of the fences was partially buried in the ground. In a number of places, more lightly constructed fences (Lichtsperren) consisting of mesh and barbed wire lined the border.[61] The fences were not continuous and could be crossed at a number of places. Gates were installed to enable guards to patrol up to the line and to give engineers access for maintenance on the outward-facing side of the barrier.[61]