▁width . ▁ ▁D ifferent ▁regions ▁have ▁made ▁minor ▁modifications ▁to ▁the ▁general ▁method ▁of ▁construction — s ometimes ▁because ▁of ▁limitations ▁of ▁building ▁material ▁available , ▁but ▁also ▁to ▁create ▁a ▁look ▁that ▁is ▁distinct ive ▁for ▁that ▁area . ▁Wh iche ver ▁method ▁is ▁used ▁to ▁build ▁a ▁dry ▁stone ▁wall , ▁considerable ▁skill ▁is ▁required . ▁Correct ing ▁any ▁mistakes ▁invari ably ▁means ▁dis ass emb ling ▁down ▁to ▁the ▁level ▁of ▁the ▁error . ▁Selection ▁of ▁the ▁correct ▁stone ▁for ▁every ▁position ▁in ▁the ▁wall ▁makes ▁an ▁enorm ous ▁difference ▁to ▁the ▁lifetime ▁of ▁the ▁finished ▁product , ▁and ▁a ▁sk illed ▁wall er ▁will ▁take ▁time ▁making ▁the ▁selection . ▁ ▁As ▁with ▁many ▁older ▁craft s , ▁sk illed ▁wall ers , ▁today , ▁are ▁few ▁in ▁number . ▁With ▁the ▁advent ▁of ▁modern ▁wire ▁f encing , ▁fields ▁can ▁be ▁f enced ▁with ▁much ▁less ▁time ▁and ▁exp ense ▁using ▁wire ▁than ▁using ▁stone ▁walls ; ▁however , ▁the ▁initial ▁exp ense ▁of ▁building ▁dy kes ▁is ▁offset ▁by ▁their ▁st urd iness ▁and ▁consequ ent ▁long , ▁low - main ten ance ▁lif et imes . ▁As ▁a ▁result ▁of ▁the ▁increasing ▁appreci ation ▁of ▁the ▁landscape ▁and ▁her itage ▁value ▁of ▁dry ▁stone ▁walls , ▁wall ers ▁remain ▁in ▁demand , ▁as ▁do ▁the ▁walls ▁themselves . ▁A ▁nation ally ▁recogn ised ▁cert ification ▁scheme ▁is ▁operated ▁in ▁the ▁UK ▁by ▁the ▁D ry ▁Stone ▁Wall ing ▁Association , ▁with ▁four ▁gr ades ▁from