With distributional hands, responder can direct the contract to a suit fit, sure in the knowledge opener has at least two of every suit.
For example, with a weak hand including six bad Hearts, responder can Jacoby Transfer opener to Two Hearts and then pass, confident of at least an 8 card Heart fit. That will be a better contract than 1 NT virtually every time.
N
S
1NT
2¨*
2©
P
Jacoby Transfer to 2 Hearts. P is a bail out. South might have only 3 or 4 points.
North
South ª Kxxx
ª Jxx © Qx
© KJxxxx
¨ Axx
¨ x
§ AKxx
§ xxx