sandpaper is used to smooth the surface objects & sandpaper is a kind of tool for smoothing objects ->  sandpaper is a tool for smoothing the surface objects  an engineer constructs a prototype from wood & a prototype is a kind of object ->  the wooden prototype is a kind of object  sandpaper is a tool for smoothing the surface objects & the wooden prototype is a kind of object ->  sandpaper can be used to smooth the surface of the wooden prototype  sandpaper can be used to smooth the surface of the wooden prototype & the engineer needs a tool to smooth the surface of the wooden prototype -> the engineer can use sandpaper to smooth the surface of the wooden prototype