Playing Acol, you may have a problem as responder with a
balanced 10 count, if you are unable to bid a four card suit at
the one level, since 1NT shows 6-9 except over 1
, and the 2NT rebid shows 11-12. You are also
in difficulty with a balanced 3334 hand with 6-7 points if
partner opens 1, when a raise in clubs
takes you past what may be the best contract of 1NT. This can
be true of both minors if you are playing "inverted minor"
raises.
All these problems can be solved by making all 1NT
responses 6-10 points, (which also means that a 2 level
response can show at least 10 points and a good 5 card suit or
11 points with a 4 card suit). With this wider range, if opener
wants to make a game try, 2 can be
used as a conventional enquiry.
In response, 2NT shows 9-10, a 3 level bid shows 8-9 with a six
card suit, and 2 bids 6-8 points, with 2 of major = 3 card support
for partner or 2
= 5 cards if partner
opened 1
, and 2
= none of those). 2 is rarely missed as
a natural bid (2 followed by
3 is "I wish I'd never heard of
`Wraight'"). The convention often proves useful, both to bid
some simple hands which are otherwise surprisingly difficult,
but more importantly to be able more frequently to stop in 1NT
when this is the right spot.