The second diagonals will already consist of two parts: the wedge rests against a corner, an opposite end face of a straight line and is strictly perpendicular the first diagonal.
The forward end face of an armrest can be made rounded off, besides in the presence of the tool. The distant end face is narrowed to 5sm that it was accurately joined from a resistant back.
It was necessary to make armrests. For them we take a board 2,5×10, length 50sm. At first we will make a template of a cardboard by the sizes provided in drawing below.