cencio, on 2021-January-29, 14:04, said:
My question is when to show my fifth suit and when to abandon. Are there some rules?
For the most part, you should not rebid a 5 card suit with minimum hands unless partner forces you to bid and all your other bids are worse / mis-describe your hand by agreement. Common situations where you are forced to rebid a 5 cd suit:
- you respond 1 of a major, partner reverses (e.g. 1c-1h-2d, 1c-1s-2h) showing a strong hand and promising a 3rd bid. It's common to rebid a 5 cd suit here as it's economical and doesn't take room, partner has promised to bid again, so you don't take a risk of ending in a 5-1/5-0 fit by rebidding.
- you open 1 of a major, partner bids a 2/1 bid (e.g. 1s-2h-2s, 1h-2d-2h, 1s-2d-2s). It's again common to rebid 5 cd suit (even of terrible quality), because again partner is bidding again (with many playing it as GF these days), it's economical, and again you should be able to avoid 5-2/1/0 fits in the subsequent auction. This is done so higher bids can be better defined. If you require 6 cd suit to rebid your suit on this auction, one has to do arguably inferior things like make high reverses (1s-2h-3d) on totally min hands, or rebid 2nt on off-shape hands with unstopped shortages, which can wrong-side eventual 3nt contracts.
- you open 1c, partner responds in your stiff, and you have an agreement that rebidding 1nt promises at least a doubleton in partner's suit, and your hand isn't strong enough to reverse.
In practically all other situations with minimums, there are better alternatives, usually involving either bidding NT, a second suit, raising partner on 3 cds (even though they might only have 4), or taking a preference to partner's first suit.
If you are strong enough, GF values, or invational values over a 1nt rebid, you can force partner to show 3 cd support by employing gadgets like 4th suit forcing, new minor forcing, xyz, xynt, checkback stayman, etc. depending on the auction. But still you aren't rebidding the suit directly in these situations.
The only real exception to this rule is when the auction has gone 1m-1M-1nt, and partner promises a doubleton (some people agree 1nt is allowable on singleton, which has pros and cons). In this situation, with shapely hands and min (not strong enough to employ xynt/nmf/whatever gadget you have agreed with inv+), it's often advantageous to rebid 2M on 5 cds. Because partner will have 3 cd support quite often, and these play better in the major, and even on the 5-2 fits the major sometimes does better.
So 1nt on first.
The second hand I'd pass since 5332, but I would rebid spades with more shape.
In other situations, where partner doesn't have to have any cards in your suit, you shouldn't rebid 5 cd suits because partner should be often passing with singletons/voids, because you are doing the same thing with good 6/7 cd suits and bidding more is just making things worse. Playing 5-1 fits on a regular basis doesn't tend to work out well.