  The chromoelectric and chromomagnetic fields, created by a static
gluon-quark-antiquark system, are computed in the quenched approximation of
lattice QCD, in a $24^3\times 48$ lattice at $\beta=6.2$. We study two
geometries, one with a U shape and another with an L shape. The degenerate case
of the two gluon glueball is also studied. This is relevant to understand the
microscopic structure of hadrons, in particular of hybrids. This also
contributes to understand confinement with flux tubes of the chromoelectric
field, and to discriminate between the models of fundamental or adjoint tubes.
