from AMBRA System in Brideguys
GAR is a relay mechanism to get shape. Whenever opener or responder shows a 5-4 distribution, 2NT is relay asking clarification.
Responses are: 3
shows 5-4, 3
shows 6-4.
In case that 5-5 and 5-4-4 distributions are still possible too:
3
shows 5-5 and high singleton, 3
shows 5-5 and low singleton and 3NT shows 5-4-4.
After the responses of 3 and 3, partner can bid:
1° STEP = generic RELAY
2° STEP = RELAY + fixes the higher suit
The responses to these relays are:
1st step: 2-2 in remaining suits,
2nd step: high singleton,
3rd step: low singleton.
After the sequence above: 1-1, 2-2, 2NT GAR cannot be invoked with 2NT, so we must use 3 and all subsequent bidding is 1 step higher.
When opener has not limited his hand yet, the GAR convention works a bit different:
3: 5-4, 11-15
3: 6-4, 11-21
3: 5-4-2-2, 16-21
3: 5-4, high singleton, 16-21
3NT: 5-4, low singleton, 16-21
After the 3 response, and the successive RELAY3 we respond:
3: 11/15 HCP, high singleton
3NT: 11/15 HCP, low singleton
4: 16/21 HCP, high singleton
4: 16/21 HCP, low singleton
Keep in mind that the 2NT bidder is attempting game, opposite a minimum a partscore is still possible.
Is not sure what ‘GAR’ means, possibly something Italian, but it would be a suitable abbreviation for ‘Game Attempt Relay’.