A building line or building setback line will usually appear on building plans. The setback line restricts building or improving the area behind or within the designated boundaries. Zoning laws typically designate these building lines in order to insure conformity and uniformity within a subdivision or development. The most common setback line is used to designate the distance a building must be built from streets, right of ways or other property lines. Occasionally, some encroachment is made on these setback lines due to irregularly shaped lots such as corner lots or cul-de-sacs. A "building envelope" is another type of setback line that establishes a perimeter around developments or subdivisions to insure that further building or improvements are not made. Due to the large size of the buffer zone surrounding an entire development, encroachments are made less often upon this type of setback.