Properties of ferroelectric domain walls are attractive for future nano- and optoelectronics. An important element is the potential to electrically erase/rewrite domain walls inside working devices. Dense domain wall patterns, formed upon cooling through the ferroelectric phase transition, were demonstrated. However, room temperature domain wall writing is done with a cantilever tip, one domain stripe at a time, and reduction of the inter-wall distance is limited by the tip diameter. Here, we show, at room temperature, controlled formation of arrays of domain walls with sub-tip-diameter spacing (i.e., inter-wall distance down to approximate to 10 nm). Each array contains 100-200 concurrently formed walls. Array rewriting is confirmed. The method is demonstrated in several materials. Dense domain pattern formation through a continuous electrode, practical for potential device applications, is also demonstrated. A quantitative theory of the phenomenon is provided. (C) 2015 AIP Publishing LLC.