Nuts and bolts can help children develop their fine motor skills (e.g. different finger grips, grasping objects and finger strength) as they play.
Using these nuts and bolts toys can also teach spatial skills. Spatial awareness is a complex mental skill which allows children to understand their own location, and the location of objects in relation to their bodies. In understanding this, children then come to learn concepts such as direction, distance and location.
NOTE: Children can easily choke on small objects, therefore you should always follow the suppliers recommended age bracket when choosing toys (especially those with small parts or pieces that could come loose).