1 —

Construct square A drawn to scale.

2 —

Calculate the distance of 17cm from the middle of square A base downwards. Determine point a.

3 —

In the upward direction, draw a vertical line of 1.70m from bottom to top of point a and mark point b.

4 —

Construct a square with the same dimensions of square A on the line constructed between points a and b. See square B in figure 4.

5 —

Draw a horizontal line crossing the two squares at point b height.

6 —

Draw a diagonal line from point c to point d (see figure 4).

7 —

From the vertices of square A, draw lines that vanish in point b.

8 —

Determine point f at the intersection of the lines that join points e, b, c and d.

9 —

By joining points f and g with a horizontal line we will have a horizontal plane.