  We show, through a simple patchy reconnection model, that retracting
reconnected flux tubes may present elongated regions relatively devoid of
plasma, as well as long lasting, dense central hot regions. Reconnection is
assumed to happen in a small patch across a Syrovatski\'i (non-uniform) current
sheet (CS) with skewed magnetic fields. The background magnetic pressure has
its maximum at the center of the CS plane, and decreases toward the edges of
the plane. The reconnection patch creates two V-shaped reconnected tubes that
shorten as they retract in opposite directions, due to magnetic tension. One of
them moves upward toward the top edge of the CS, and the other one moves
downward toward the top of the underlying arcade. Rotational discontinuities
(RDs) propagate along the legs of the tubes and generate parallel super-sonic
flows that collide at the center of the tube. There, gas dynamics shocks that
compress and heat the plasma are launched outwardly. The descending tube moves
through the bottom part of the CS where it expands laterally in response to the
background magnetic pressure. This effect may decrease plasma density by 30 %
to 50 % of background levels. This tube will arrive at the top of the arcade
that will slow it down to a stop. Here, the perpendicular dynamics is halted,
but the parallel dynamics continues along its legs; the RDs are shut down, and
the gas is rarified to even lower densities. The hot postshock regions continue
evolving, determining a long lasting hot region on top of the arcade. We
provide an observational method based on total emission measure and mean
temperature, that indicates where in the CS the tube has been reconnected.
