Answer by  
                                                                                          nnlin (53)
                                                            
                          
                          
                                                          You can use a bubble meter, which is a tube full of water and air. When the meter is placed on the floor horizontally, it will show the higher side by having the bubbles float to one side. When it is level, the bubbles will be exactly in the middle. Most meters are marked the exact middle for precise leveling.