How will you store your favourite things?
3
Adding latches and catches
Some of the more ambitious children may wish to include latches or catches in their containers to prevent accidental opening. Here are some possibilities.
Fix a paper fastener through the front face of the container and place a hole in the flap so that the prongs of the fastener go through the hole in the flap. This catch is closed by opening out the prongs and opened by closing them together. Careful measuring is required to get the hole and the fastener in the correct places.
Use a treasury tag in a similar way to the paper fastener. 
Pass it through a hole in the front face of the container and through a hole in the flap. This does not require such precise alignment, especially if you use a long treasury tag. In both the above cases it will be worth reinforcing the edges of the holes with self-adhesive ring binder supports.
You can use a thin elastic band to hold the lid shut. 
When the lid is opened the elastic band is stretched even more and the lid has to be held open to prevent it snapping shut. Both the lid and the floor of the container will need reinforcement where the elastic band is attached. It is possible for a child to design a prop that will keep the lid open even though the stretched elastic band is providing a force that is trying to shut the lid.