  As true as it is that a bricklayer needs a plumb line and a T-square, so it
is that a physicist using general relativity needs how to draw geodesics and
use fields of congruent vector frames of reference. While the first part of the
preceding statement depends on the Christoffel connection and related metric
and curvature concepts, the second part depends on the Weitzenb\"{o}ck
connection and the concept of torsion. This dual structure has been considered
before as a possibility of using either one of them to describe General
relativity. We claim here that both structures have to be correlated to produce
useful interpretations of any space-time model.
