[Fluffy]

I am a bit lost when it comes to competitive auctions after opening strong club

a typical example is this


1♣-(3♠)-pass-(4♠)

what kind of hands would double, do they show extras?, and what kind of hands would pass?

Also what kind of hands would responder have for balancing with a double (or with a suit).

[Flameous]

I would start doubling with 2-3 points above minimum and good t/o shape. I'd pass with all of my first balanced range whatever it is, and minimum of the second range, and double with stronger. So I play 15+ club, but first NT range is 16-18, second 19-21, I'd have either good T/O with 17+ (could be two suited occasionally) or 20+ flat for a double.

Partner's double shows values but couldn't bid over 3♠, so usually flattish hand. This is almost always left in.

[JLOGIC]

You are not in a forcing pass. I recommend that you double with short spades + prime cards and/or extra values, and pass with spade length. I mean x AKxx Axxx AJxx is a minimum 1C but its obviously a double. Form of scoring/vulnerability matters. It is not that much different than handling 3S p 4S immediately, except you can more comfortably pass with 3244 19 or whatever.

The times you have a doubleton spade will be the hardest to judge, and the nature of your high cards/how much extra you have/vulnerability will matter a lot. If you play a strong 2N opener these situations will be easier.

[Fluffy]

4NT would still be 2 suited for both players right?

The weak hand might have 2 kind of hand for reopening with double the way we play it: a 8+ hand with wrong shape for a take out double of 3♠, or a maximum 6-7 hand akin 1444, wich of them it is?

[dake50]

Partner's pass over 3S said 'not hearts' -- does that help?
That's my agreement for just this expectable auction.
Also 1C has spades, as 1D has hearts.