In some places, villages adjoining the border were fenced with wooden board fences (Holzlattenzaun) or concrete barrier walls (Betonsperrmauern) standing around 3–4 metres (9.8–13.1 ft) high. Windows in buildings adjoining the border were bricked or boarded up, and buildings deemed too close to the border were pulled down. The barrier walls stood along only a small percentage of the border – 29.1 kilometres (18.1 mi) of the total length by 1989.[1]