Dig-Out

Dig-Out is a bidding method after your side opens 1NT and the opponents double for penalty. It emphasizes the spade suit, with immediate 2// bids showing 2-suiters with spades. This theoretically maximizes the opportunity to locate spade fits and consume the enemy's bidding space.

Partner Opp 1 You Opp 2

1NT X ?

Partner Opp 1 You Opp 2

1NT Pass Pass X

?

After the opposing double, the runouts are:

Pass Requires partner to make an artificial redouble. Shows a two-suiter without spades:

Clubs and diamonds (4-4 or better). After partner's redouble, bid 2. Partner can pass or correct to 2.
Clubs and hearts (4-4 or better). After partner's redouble, bid 2. If partner tries correcting to 2 (see above), rebid 2.
Diamonds and hearts (4-4 or better). After partner's redouble, bid 2.

XX Requires partner to bid an artificial 2. Shows a one-suited hand. With clubs, simply pass partner's 2 bid; otherwise, correct to 2/ with a 5-card suit.
Alternatively, opener can make the following rebids instead of redouble (to consume bidding space while still following the Law of Total Tricks):

2 shows 4+ clubs. Responder can correct to 3.
2 shows 4+ clubs and diamonds. Responder can correct to 3/.

2 Shows clubs and spades (4-4 or better). Partner can pass with club tolerance, or correct to 2 with longer spades.

2 Shows diamonds and spades.

2 Shows hearts and spades.

2 Natural, 5+ spades, signoff.

2NT 5-5 or longer in the minors.

3x Preemptive, 6-7 card suit, signoff.

Opener's alternative rebids after responder redoubles have been termed "paradox" bids, which are artificial bids of "a suit you haven't got in response to a conventional bid that shows ambiguously one of two suits."

Origins

Dig-out was created by British expert Chris Ryall.

Pass	Requires partner to make an artificial redouble. Shows a two-suiter without spades: Clubs and diamonds (4-4 or better). After partner's redouble, bid 2. Partner can pass or correct to 2. Clubs and hearts (4-4 or better). After partner's redouble, bid 2. If partner tries correcting to 2 (see above), rebid 2. Diamonds and hearts (4-4 or better). After partner's redouble, bid 2.
XX	Requires partner to bid an artificial 2. Shows a one-suited hand. With clubs, simply pass partner's 2 bid; otherwise, correct to 2/ with a 5-card suit. Alternatively, opener can make the following rebids instead of redouble (to consume bidding space while still following the Law of Total Tricks): 2 shows 4+ clubs. Responder can correct to 3. 2 shows 4+ clubs and diamonds. Responder can correct to 3/.
2	Shows clubs and spades (4-4 or better). Partner can pass with club tolerance, or correct to 2 with longer spades.
2	Shows diamonds and spades.
2	Shows hearts and spades.
2	Natural, 5+ spades, signoff.
2NT	5-5 or longer in the minors.
3x	Preemptive, 6-7 card suit, signoff.