After a 1NT opening, the opp overcalled. How does the responder bid?
The opp can overcall by naming a suit or by doubling.
The responder :

uses the 'Rubensohl' convention after and over in a suit ( 2 ♦, 2 ♥ or 2 ♠) :
- all bids by the responder at level 2 are natural and non forcing
- from 2NT up ,all bids are transfers until 3 ♥ (transfer for ♠). 2NT is therefore artificial : transfer for ♣
- The impossible transfer is a Stayman
- The double is take-out : It can be a Stayman with just 8H or show a regular 8+HCP hand .
After a double 'Major-minor' : the responder, on the first rounds bids as if there had not been a double:
- 2 ♣ is a Stayman
- 2♦, 2 ♥ et 2 ♠ are transfers
- NT bids are natural
- a redouble is for penalty

S	W	N	E

Problem E5867 2 ♥ natural bid, that shows 5 cards in ♥ and a hand with a maximum of 7HCPs.

S	W	N	E

Problem E59982 ♣ Stayman. After your partner opened 1NT, do not take into account the 'double' in the first round of bidding.

After a 1 NT opening, the LHO overcalled.
Après une intervention naturelle à 2 ♦, 2 ♥ or 2 ♠

all bids by the responder at level 2 are natural
from 2NT up ,all bids are transfers until 3 ♥ (transfer for ♠). 2NT is therefore artificial : transfer for ♣
The impossible transfer is a Stayman
The double is take-out : It can be a Stayman with just 8H or show a regular 8+HCP hand .
A 3♠ bid is an invite to game at 3NT, if the opener olds the suit of the overcall .