The RVs use a 2x2.5x3/16" angle, trimmed to fit into the nose. See the pic of left wing root nose. An .063" doubler goes on the inside of the root rib; the angle goes on the outside, facing the fuselage. A similar angle (aluminum in early kits, steel in later kits) mounts to the fuselage side at an interior bulkhead. The overlap gets a single bolt. In the RV kits, the root nose rib is also the end of the fuel tank. Because crash impact can drive the wing aft, pulling the nose away from the fuselage, one of the tabs gets a horizontal slot instead of a hole. This allows the joint to slide apart instead of ripping the end out of the fuel tank. In normal operation, the bolted joint is loaded only in vertical shear, so a horizontal slotted joint has no effect in normal operation.