[billw55]

In common use, do support doubles apply in a 2/1 auction? For example,

1♠ - p - 2♥ - 3♣
X - p - ?

Should this be simple penalty, or support, or something else? Presumably responder has already shown 5+ hearts, so is there there any need to use a support double? Any difference if responder bid 2♦?

[ArtK78]

Typically, support doubles apply only through 2♥. I suppose they can be applied at a higher level, but given that you have to play somewhere after you double, that can be a problem.

[Phil]

It would be unusual to play support doubles here. In a 2/1 auction, doubles are typically penalty, but it might be better for a double to be 2-3 in their suit and pass is short or a true trap.

[SteveMoe]

Support doubles typically apply through 2♥ for Law of Total Tricks reasons - you don't want to get stuck playing a 4-3 fit at the 3 level when strength is equally distributed and there's no shortness in the 3-card trump hand.

After partner's 2/1 bid, a double here is Balance of Power (See Mel Colchamiro's Book) and requires only 3 trump if intervenor's (opponent) bid is at the 2 level and 2 trump if at the 3-level (Mel's rule of 23).

Red vs White you have to decide if your side's putative game is worth more than the double.