If I was trying to build a garden shed, categorise each of the following as either "useful" or "not useful". A banana,  a hammer, nails, screws, personal protective equipment, an assistant, wood, kitchen knife, spoon, ice, magnifying glass
The following items would be "useful" to help you build a garden shed: 

A hammer
Nails
Screws
Personal Protective Equipment 
An assistant 
Wood 

The following items are "not useful" to help you build a garden shed: 

Banana
Kitchen knife 
Spoon
Ice 
Magnifying glass