English: The model base for the design and sizing of symbols.

Standard as specified by the Official Journal of the European Union: The model base consists of: 1. a base 50 mm square, this dimension being equal to nominal dimension ‘a’ in the original;
2. a base circle 56 mm in diameter having approximately the same area as the base square (1);
3. a second 50 mm-diameter circle is drawn within the base square (1);
4. a second square the tips of which lie on the base circle (2) and the sides of which are parallel to those of the base square (1);
5. and 6. two rectangles having the same area as the base square (1), their sides being at right angles to each other and each of them devised so as to divide the opposite sides of the base square into symmetrical points; [62.5mm by 37.5mm.]
6. a third square the sides of which pass through the points of intersection of the base square (1) and the base circle (2) and are inclined at 45°, thus providing the greatest horizontal and vertical dimensions of the model base;
7. an irregular octagon formed by lines inclined at 30° to the sides of the square (7).

The base model is laid upon a grid the lower side of which measures 12,5 mm and coincides with the base square (1).