The length required for the ladders was thus obtained, being calculated from the breadth of the brick.
Now the wall of the Peloponnesians was constructed as follows.

It consisted of two lines drawn round the place, one against the Plataeans, the other against any attack on the outside from Athens, about sixteen feet apart.

The intermediate space of sixteen feet was occupied by huts portioned out among the soldiers on guard, and built in one block, so as to give the appearance of a single thick wall with battlements on either side.

At intervals of every ten battlements were towers of considerable size, and the same breadth as the wall, reaching right across from its inner to its outer face, with no means of passing except through the middle.

Accordingly on stormy and wet nights the battlements were deserted, and guard kept from the towers, which were not far apart and roofed in above.
Such being the structure of the wall by which the Plataeans were blockaded, when their preparations were completed, they waited for a stormy night of wind and rain and without any moon, and then set out, guided by the authors of the enterprise.