The square is a template in the shape of an isosceles triangle that is used in technical drawing.[1] It can be of different sizes and colors or have bevels on the edges that allow it to be used with a rapidograph. It has one 90° angle and two 45° angles. It is usually used, together with a bevel or a ruler, to draw parallel and perpendicular lines. It can be made of various materials, although the most common are: plastic and wood.

The square has the shape of an isosceles right-angled triangle. It is obvious that two equal squares, placed together by the hypotenuse, result in a square.

The legs of the square are the sides of the square, and the hypotenuse is the diagonal; The proportions between the legs and the hypotenuse are determined by this relationship.

If it is established that:

and by the Pythagorean theorem:

It is concluded that:

If it is established that:

Therefore, the two legs are equal and their acute angles measure 45°.

Given the shape of the square, it has immediate use for drawing perpendicular lines and lines inclined at 45°. These inclinations are used in the knightly perspective. To do this, a ruler inclined at 45° is placed as a reference to support the square on the appropriate side according to the inclination of the line to be drawn.

The lines of flight of the knight's perspective are drawn perpendicular to the ruler. If the coordinates of a point are placed on the axes, making the parallels corresponding to the axes, it is located at a point in space, according to the chivalric perspective.

In the same way, the military perspective can be drawn with the horizontal axes at 45°. By placing a horizontal ruler, you can draw the vertical axis and both of the horizontal plane at 45°; By placing the coordinates on the corresponding axes, it is laid out according to the military perspective.