Because it's an impossible and
expensive job, to apply through-hole-plating the chemical
way on 2-layer prototypes and small series, we have chosen
the mechanical way. Holes that can not be
soldered easily on the component side, will be filled with
a brass cylinder (revit). We apply this on hole sizes of 0.8
and 1.0 mm only.
On larger holes, the connection
can be made another way. We drill a small hole on the edge
of a pad through which you can put a a piece
of wire. Then you can solder on both sides of the PCB.