Weak Equals Jump.  With weak (0-7 HCP) hands but long (6+ card) suits, responder should make weak jump shift calls.

These are preemptive, but also warn opener of the situation.

They may be made in any suit including the majors. Such hands must be useless with other than the bid suit as trump.

Obviously the suit or hand can't be any good, else normal bids would apply.

N	E	S
1§  . . .	P	2© *	Weak, 6+ Hearts, preemptive.
1§ . . .	P	1©	Not  weak. 4+ Hearts and unlimited.
1§   . . .	P	2¨ *	Weak, but in Diamonds.
1¨   . . .	P	2§ *	A Two Over One game forcing bid. Definitely not weak.