After a 3rd or 4th seat major opening, a 2 response is used to show a limit raise (10-11) and asks partner if their opening was sound or light.
Opener responds:
Over a 2 rebid, responder rebids the major to signoff.
After:
1 | 2 | ||
2 | ? |
Responder can rebid 2 to checkback for a better 4-4 heart fit. Without a heart fit, opener returns to 2