This depends on the age of the child.  If it is a child in the Casa, either redirect them to a different activity or sit with them and ask to work with them, trying to ascertain what experience they are trying to give themselves.  Think of some legitimate way the child’s need/interest can be served.  Be clear that certain things are used for certain activities only but, suggest something else to use for the needed experience, if appropriate. 

If it is a Casa aged child – or older, try to discern if the child is bored with the material and therefore doing something more “creative” with the materials – OR if the material is too difficult for the child.  Based on the observation, a new activity can be presented that more accurately meets the needs of the child.

If it is a young child, under 2.5 years, observe to see what they are doing with the material.  Often they use material to show their understanding of the use of things – which we often misinterpret as “playing with the material.”  If no damage is being done, continue to observe, noting how much time is spent doing whatever the child is doing, and observing if the child is using language in her “work”.  Again, try to ascertain what need the child is trying to satisfy and if there is a different way to satisfy that need.  Sometimes when a young child is unengaged they need an adult to sit with them, and work with them, encouraging them to gradually take over the work being done.