Aardvark:

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An add-on you could use as well as playing Halmic is part of the "Aardvark" system.  This uses bids of 2♠ and 2NT to show 5-5 shaped hands (other variations can also be used if you wish to look them up on the Internet).

With a 5-5 shape including spades, you can bid 2♠.  Partner leaves this in with 3(+) spades and bids 3♣ with only 2S as a pass or correct bid.

A 2NT bid shows two 5-card suits that do not include spades.  Partner bids his longest (3+ cards) minor and responder will either pass or convert to Hearts if he does not have the suit opener has bid.

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So summarising, after a double of 1NT :

• 2♠ = 5/5, Spades and another

• 2NT = 5/5 two suits not Spades

Easy really...