[peachy]

There were some remarks made about NT openings and ACBL regulations in another thread.

One can have the agreement to open 1NT if it is *strong (15+) and forcing* with no shape restrictions. That of course is alertable.

However, I cannot find what the ACBL regulation says about having an *agreement* to allow singleton in *natural* 1NT opening. Would it be correct to assume it is legal if it is alerted? What about natural 1NT overcalls? Same thing?

[hrothgar]

Here's the "simple" version

There is nothing in the GCC that sanctions (allows) a 1NT opener that, by agreement, could include shapes like 4=4=4=1, 4=3=5=1, etc.

At the same time, players are always allowed to exercise judgement and make minor deviations. Assume for the moment, that you and your partner have the agreement that a 1NT opening shows

~ 15 - 17 HCP
4432, 5332, or 4333 shape

You get dealt the following hand

♠ KQxx
♥ KQxx
♦ KT9x
♣ K

You are allowed to exercise judgement, violate your agreements, and open this hand 1NT.

You will, however, run into trouble if you do this frequently enough that 4=4=4=1 shape with a stiff honor becomes an implicit agreement.