Height Functions in CES

 In a CES, a (global) height function no longer makes sense, but one can define height functions locally. Classically, a surface is tight provided every height function has exactly one maximum, and this corresponds to the two-piece property. In CES, a surface with \chi\le 0 is tight provided every (local) height function has no maximum. In a sense, these surfaces have a "one-piece property".