Care should needs to be taken when amendments are based on details which may only be derived from the schematic drawings of the original application (see also H‑IV, 2.4).
In particular, a figure which serves only to give a schematic explanation of the principle of the subject-matter of the invention and not to represent it in every detail does not allow the conclusion that the disclosed teaching purposively excluded a feature not represented (T 170/87).
The manner in which a particular feature is depicted in the drawings may be accidental. The skilled person must be able to clearly and unmistakably recognise from the drawings, in the context of the whole description, that the added feature is the deliberate result of the technical considerations directed to the solution of the technical problem involved.
For example, the drawings may depict a vehicle in which approximately two thirds of the height of the engine is located below a plane tangent to the top of the wheels. An amendment which defines that the major portion of the engine is located below the given level would not infringe Art. 123(2) if the skilled person would recognise that such a spatial arrangement of the engine with respect to the wheels is in fact a deliberate measure directed to the solution of the technical problem (see T 398/00).