RKCB

Asking about 3^rd control in side suit

After RKCB we bid 6 in a suit below trump. This way we are asking about 3^rd round control in the suit bid (Q or xx). 

Without the 3^rd round control partner bids 6 in the trump.

With the Queen, partner bids 6NT.

With a doubleton, partner bids 7♣.