11. He said the dust helps create a firm, level surface while the pebbles provide drainage. 12. This provided a level surface for mechanically changing the vehicle from rail to road wheels. 13. For example, a level surface in three-dimensional space is defined by an equation of the form. 14. The interior floor of Stefan is a generally level surface that is marked by several impacts. 15. Repeated beds will often be scratched to a nearly level surface , about two meters in diameter. 16. Water will run off a level surface . 17. Stock certificates were left for weeks piled haphazardly on any level surface , including filing cabinets and tables. 18. Shims are typically used in order to support, adjust for better fit, or provide a level surface . 19. _Place the grill on a level surface . 20. The interior floor of this crater forms a relatively level surface that is marked by several small craterlets.
