wheels are a part of roller skates & a roller skate is a kind of vehicle -> a housing spots is a mean of appalachian with year a roller skate is a kind of vehicle with wheels  a roller skate is a kind of vehicle with wheels & a wheeled vehicle is a kind of vehicle with wheels -> a steels astronomers is a mean of wheeled protection a roller skate is a kind of wheeled vehicle  a roller skate is a kind of wheeled vehicle & a wheeled symbols requires rough spoon -> a roller skate requires smooth surfaces a roller skate requires smooth surfaces  blacktop is made of asphalt concrete & asphalt has a smooth surface -> a pond has a rough bottom a blacktop has a smooth surface  a roller skate requires smooth surfaces & a pond has a rough bottom -> a roller skate can be used on a blacktop surface