The wads are cut oversized, a bit, or at least are cut to be a tight fit. Second, OP wads are usually 1/8' thick, while cushion wads can be 1/4 or 1/2" thick. Finally, the Over shot cards are about .025" thick. You use a wide shaped jag on your rod to load these components, and the friction between the sides of the bore, and the sides of the wads is enough to offer enough resistance to the jag that they are driven down the barrel straight. You want a bore diameter jag on the rod so you can protect those edges, as the whole purpose of the wad is to SEAL gases behind the wad. You can roll the edge of the wad in a shallow dish of oil, or rub some thicker "moose snot" on the edges of the wad, to grease the barrel loading and shooting the wads. If you use the thicker Moose snot, it does not contaminate your powder as oil will.
you also can load with only OS cards, using 2-4 cards in place of the OP wad, and two OS cards on top of the shot. One will generally do, but using two is a good habit to get into, to be sure that the shot load does not move forward, possibly turning the card, and spilling your shot out of the gun while walking in the field. Using 2 cards is often done when shooting DB shotguns, to keep the load in the second barrel from shifting forward as the result of the recoil of firing the first barrel. If you poke off-center holes in these OS Card with an awl, it lets air get through the cards so they separate, and quickly fall to the ground close to the muzzle of your gun, rather than follow the shot in the air, and bump it. Bumping is believed to be the process that creates " donut hole " patterns. This is most often seen when 1/2" cushion wads are used that are lubed. They weigh so much they follow the shot and bump the back of the shot column in the air, causing a hole to appear in the middle of the pattern. Its not uncommon to see the cushion wad fly further than a 25 yard patterning board, putting a big hole through the paper.
