Holding device

A system comprising at least a first and second element, said elements being three-dimensional and each element comprising:

• a centre point in said element;
• at least one face coupled to said centre point and said face comprising:
• holding means, adapted for interacting with a functionally aligned holding means of a similar element, and comprising a holding state and a released state, said holding means in said holding state engaged with said aligned holding means of said similar element for holding said element positioned with respect to said similar element, and in said released state disengaged with said aligned holding means, and
• sensing means comprising a position sensor for sensing a position of said face of said similar element on said face of said element, said position sensor comprising an emitter for emitting electromagnetic radiation in an emitter pattern, a receiver for said electromagnetic radiation comprising detector elements in a receiver pattern, and said emitter pattern and receiver pattern mutually oriented for providing an alignment indication when said holding means are aligned with holding means of said similar element and said face is at a predefined orientation with respect to said face of said similar element,
• wherein said sensing means is functionally coupled to said holding means, and wherein said holding means takes said holding state when said sensing means provides said alignment indication.