Oh, I see. Yes, while it's best to dimple separately, you can dimple thin stock together. It is also possible to countersink thick stock and dimple thin sheet over it, using the countersink as the female die, though I've only had to do that once due to an error I made while assembling. It was either that or drill out a lot of rivets so I could dimple the few holes I'd missed. Drilling carried a lot of potential damage while dimpling in place only meant a less crisp dimple.
Patrick Kelley - Flagstaff, AZ
RV-6A N156PK - Flying too much to paint
RV-10 14MX(reserved) - Fuselage on gear
EAA Technical Counselor #5357