The Unusual NT bid is used to show a 2-suited hand. When opponents open on the 1 level and you jump to 2nt you are telling your partner that you have 5/5 (or better) in the two "lowest" un-bid suits. Some partnerships agree it is for takeout in the minors only, however, this is less effective. Once your partner has chosen a suit you should not bid again unless you have extra values or extraordinary shape.

Some experienced players agree that an Unusual Jump or bid of 4nt at the first opportunity shows a great hand in the minors and asks for a takeout at the five level.

Sandwich Notrump has essentially the same purpose as Unusual Notrump but is made at the one level after both the opponents have bid and your partner has passed. It implies a weaker distributional hand with 5/5 in the two unbid suits. The name derived from the fact that you are "sandwiched" between the opponents.

Hand 1

Partner	3 J7 AJ876 A9864
Opener
	T8 T976 QT9 KQ52

North	East	South	West
-	-	-	1H
2NT*	Pass	3C*	Pass
Pass	Pass	-	-

West opens the bidding 1H and your partner overcalls 2nt. She is showing a two suited hands with 5/5 in the two lowest unbid suits -- in this case clubs and diamonds. This bid is obstructive since without invitational strength it is difficult for the opponents to compete.

With decent clubs you take a preference
for that suit. Since you are relatively weak you make the cheapest bid you have available.

Hand 1

Partner 76
J7
AJ976
A9864

Opener

You KJ32
K8632
KQ3
T

North

East

South

West

Pass

1H

Pass

Pass

2nt*

Pass

Pass

3D

Pass

Pass

Pass

-

Your RHO opens 1H. You have values but with your holding in hearts and your shortness in clubs you cannot bid. Your LHO opponent also passes. Partner (who has already passed) now bids 2nt*.

You recognize this as the Unusual Notrump asking for a takeout in one of the two lowest unbid suits and so you bid 3D.

Points of Discussion -- Many partnerships take a mini-maxi approach when using this convention -- either having
less than an opening hand or 17+ points. If partner takes a preference bid -- opener will not bid again unless he has extras.
If partner cuebids the opponent's bid he is showing game/slam interest -- it is forcing. Conversely, if partner bids an
independent suit -- it is not forcing and indicates that he has a long suit of his own and lacks support for your suits.
A response of 3nt is to play and a response of 4nt is blackwood.

References:                                                                           Quiz on the Unusual Notrump

Richard Pavicek's Great site -- a fun quiz on the unusual notrump

Karen Walker's site --detailed discussion of the uses of  Michaels and the Unusual Notrump

Fifth Chair Archives -- excellent article by Stan and Louise Dorn on the Unusual Notrump especially notible is the distinction between an unusual notrump in the direct seat and a balancing notrump .

Pattaya Bridge Site -- description notes on Sandwich Notrump