jeweler, not to take your question away from Joe, but "weep holes" are exactly that...to let moisture that has gotten in between the top or bottom rib. Mostly the bottom rib. It is usually just after the for-end hanger or loop.
It is very important to make sure this moisture is out from between the ribs when you do your final rusting as the water can weep out and stain that area. Always a good idea to have the barrels with the bottom rib down and at a slight angle to let any water out.
When I do mine I usually use a propane torch and lightly heat the barrels to dissipate any moisture.
Since I only do my L.C. Smith's, they all have this weep hole from the factory, both Damascus and fluid steel.
