A hyperbolic paraboloid is an infinite surface in three dimensions with hyperbolic and parabolic cross-sections, which means it contains two families of mutually skew lines. The lines in each family are parallel to a common plane, but not to each other. 

As a doubly ruled surface, it can be used to construct a curved surface with a lattice of straight beams, hence are easier to build than curved surfaces that do not have a ruling and must instead be built with curved beams.