Minor-oriented openings

General

The minor suit openings in SPREAD all occur at the two level and show 10-14 HCP. 2C shows either a one-suited hand with clubs, or a two-suited hand with at least six clubs and exactly four diamonds. The 2D opening shows either a one-suited hand with diamonds, or a two-suited hand with at least six diamonds and exactly four clubs. The remaining hands (those with at least five cards in both minor suits) open 2NT. The five-four minors hands are included in the 1NT opening. The limited nature of these hands often makes it very easy for responder to determine that the opening side has little (or no) play for game, and responder will often take an action that is a suggestion of a final contract. Additionally the knowledge responder has of the opponents' major suit fit(s) will sometimes allow him to violate agreements for tactical reasons.
After the lower openings, natural bids in both majors, a game-forcing relay, an invitational bid, a preemptive raise and a both-minors preemptive raise would all be useful, however not all of these can fit into the available space. Thus a compromise is reached: 2NT is always natural and invitational, all raises are not invitational, Step 1 is the game-forcing relay, and the cheapest major suit bids not already used are natural. This allows 3C over 3D to be a non-invitational attempt to play in 3C or 3D according to opener's hand type, which is much more useful than a natural club-showing bid.

Responding to the 2C opening

After 2C

A game-forcing relay, natural non-forcing major suit bids, an invitational notrump bid, non-invitational raises and fit-showing jumps are available.

2D Game-forcing relay
2H 2-suited with 4D and 6+C (symmetric continuations) (impossible shapes are omitted from the structure)
2S+ 1-suited with 6+C (symmetric continuations)
2H Natural, non-forcing (5)6+H
2S 3046
2NT 7+C with broken suit and spade and diamond honours
3C Solid 7+C
3D 3H 3+D 0-1S
3H 3H minimum, balanced or 3S
3S 3S 3H 0-1D maximum
3NT Impossible
4C Solid clubs and 3H
4H 3H maximum balanced
2S Natural, non-forcing (5)6+S
2NT 7+C with broken suit and heart and diamond honours
3C Solid 7+C
3D 3S 3+D 0-1H
3H 3S 3H 0-1D
3S 3S minimum balanced
3NT Impossible
4C Solid clubs and 3S
4H 3S maximum balanced
2NT Natural, invitational
3C/4C Not invitational, wide-ranging
3D/3H/3S Fit-showing jump, 6 cards in the suit bid and 3C
4NT Both minors, requesting a 5D response when holding four diamonds
Games To play

Responding to the 2D opening

After 2D

A game-forcing relay, natural non-forcing major suit bids, an invitational notrump bid, non-invitational raises, a three-level minor-suit scramble and fit-showing jumps are available.

2H Game-forcing relay
2S 2-suited with 6+D and 4C (symmetric continuations) (impossible shapes are omitted from the structure)
2NT+ 1-suited with 6+D (symmetric continuations)
2S Natural, non-forcing (5)6+S
2NT 7+D with broken suit and heart and club honours
3C 3S 3+C 0-1H
3D Solid 7+D
3H 3S 3H 0-1C
3S 3S minimum balanced
3NT Impossible
4D Solid diamonds and 3S
4H 3S maximum balanced
2NT Natural, invitational
3C Not invitational, wide-ranging, seeking a club contract when responder has four clubs and a diamond contract otherwise
3D Not invitational, wide-ranging
3H Natural, non-forcing (5)6+H
3NT Impossible
4D Solid diamonds and 3H
4H 3H useful hand
3S/4C Fit-showing jump, 6 cards in the suit bid and 3D
4NT Both minors, requesting a 5C response when holding four clubs
Games To play

Responding to the 2NT opening

3C/3D To play
3H/3S Natural and forcing
3NT To play
4C/4D Not invitational
4H RKCB for C
4S RKCB for D
4NT Both minors, seeking opener's better suit

Competitive Bidding

When the opponents compete before a relay auction has begun, relays are not used. A redouble of the 2C or 2D opening shows tolerance to play in the current contract and interest in penalising the opponents. Otherwise, their double of our opening or their overcall of our shown suit is ignored.
At opener's first opportunity to double, when responder has been silent, double shows a maximum with 0-1 in the opponents' suit and 3+ in all unbid suits. All other doubles by opener are general takeout until either hand describes a long suit, shows a second suit, indicates balanced or semi-balanced nature, or makes a takeout double. Such doubles are for penalty.
After any raise, doubles of suit bids by responder are for penalties. A double by opener at his first opportunity strongly suggests bidding on but without the freak needed to break the captaincy held by responder.
Jump bids in new suits remain fit-showing, except where the suit bid at the previous level was not natural. Thus the auction 2D - ? - 4C is natural. Non-jump suit and natural notrump bids remain non-forcing. Raises are not constructive. Bids in the opponents suit(s) are game-forcing. In various esoteric auctions where fit is known and further competition possible, jumps (and non-jumps that can't be natural) are fit-showing to empower partner's further actions in competition.
2NT bids in competition normally show two places to play, particularly in smouldering 2-level auctions when double would be for penalties. In any case, 2NT is never natural in competition. 4NT at responder's first call asks for responder's preferred minor suit in context.
Except where already defined above, 4NT in a competitive auction is RKCB whenever that is possible, and suggesting two possible strains at the five level whenever RKCB is not a possible interpretation. An unnecessary jump to five of opener's suit asks for control of their suit (partner cuebids holding first-round control, and raises holding second-round control).
When the opponents compete after a relay auction has begun, then the agreements used are identical to those used after interference during Pass auction. In particular all doubles by relayer (and opener if relays have been broken) are for penalties.