  We revisit the static potential for the $Q Q \bar Q \bar Q$ system using
SU(3) lattice simulations, studying both the colour singlets groundstate and
first excited state. We consider geometries where the two static quarks and the
two anti-quarks are at the corners of rectangles of different sizes. We analyse
the transition between a tetraquark system and a two meson system with a two by
two correlator matrix. We compare the potentials computed with quenched QCD and
with dynamical quarks. We also compare our simulations with the results of
previous studies and analyze quantitatively fits of our results with anzatse
inspired in the string flip-flop model and in its possible colour excitations.
