# Reading a Blackjack Rule Card: Every Abbreviation Explained

A plain English glossary of blackjack rule card shorthand: S17, H17, DOA, DAS, RSA, LS, ES, ENHC, 3:2, 6:5, penetration, ASM, CSM, and the H, S, D, Ds, P, Ph chart codes.

Source: https://21trainer.app/articles/blackjack-rule-card-glossary/
Updated: September 27, 2026
Publisher: 21 Trainer, makers of Blackjack Strategy: 21 Trainer, an educational blackjack trainer for iPhone (https://apps.apple.com/app/blackjack-strategy-21-trainer/id6759527695)

> **Educational content, not gambling advice.** 21 Trainer and this article teach blackjack strategy and card counting as skills, using virtual chips only. No strategy or counting system guarantees winnings, and nothing here encourages real-money play. If gambling is a problem for you or someone you know, call 1-800-522-4700 (National Council on Problem Gambling).

Rule cards, felts and strategy charts are written in a compressed shorthand that assumes you already know the code. S17, DAS, RSA, ENHC, penetration, Ds, Ph: each stands for a full rule, condition or play, and most of them either move the house edge or change the correct play of specific hands. Our piece on [reading the felt](https://21trainer.app/articles/reading-the-blackjack-felt/) covers where to find these lines on a physical table; this glossary defines them all in one place, grouped by what they describe, with the article that covers each term in depth.

A note on the numbers. Where an entry quotes a cost, it comes from the article linked in that entry, and every figure describes the long run effect on the house edge, not on any single session.

## The dealer's side: S17, H17, peek, hole card and ENHC

**S17** means the dealer stands on all 17s, soft ones included. **H17** means the dealer must hit soft 17, a 17 that counts an ace as 11, such as ace-six. H17 costs the player roughly 0.2 percentage points per the commonly published tables, and it moves a handful of your doubling and surrender decisions, all mapped in our [S17 versus H17 comparison](https://21trainer.app/articles/s17-vs-h17/).

**Peek** describes the dealer checking the hole card for blackjack when showing a ten or an ace, before you act. Where there is no peek, you can double or split and then lose both bets to a dealer natural; the commonly published figures put the cost at roughly 0.08 percent through doubles and 0.03 percent through splits, a little over a tenth of a percent in total. The mechanics are in our piece on [the peek rule](https://21trainer.app/articles/dealer-peek-rule/).

**Hole card** is the dealer's facedown card in the American game. **ENHC**, European no hole card, means the dealer takes no second card until the players finish, which exposes doubles and splits to a late dealer blackjack and costs about 0.11 percentage points per the commonly published tables. Our article on [European blackjack and the no hole card rule](https://21trainer.app/articles/european-no-hole-card/) works through it.

## Your options: DOA, doubling limits, DAS, RSA, splits and surrender

**DOA**, double on any two cards, is the liberal doubling rule the standard charts assume. Tables that restrict it print **double 9 through 11** or **double 10 and 11 only**: per the rule effect tables Wizard of Odds publishes, the first restriction costs about 0.09 percent and the second about 0.18 percent, which our piece on [tables that restrict doubling](https://21trainer.app/articles/double-restrictions-9-10-11/) prices in full.

**DAS**, double after split, lets you double hands created by splitting. It is worth roughly 0.14 percentage points to the player per the commonly published tables, and its absence flips several low pair splits to hits. [Our DAS article](https://21trainer.app/articles/das-double-after-split/) covers both, and why the rule is easy to miss: it varies without any change to the felt. **No DAS** is the same rule switched off.

**RSA**, resplit aces, lets you split again when a third ace arrives on a split ace. As Wizard of Odds calculates, against a baseline of eight decks with the dealer standing on soft 17 and DAS allowed, permitting it is worth about 0.08 percent to the player; [our resplit aces article](https://21trainer.app/articles/resplit-aces-rule/) covers the details. **Split limits**, how many times a pair may be resplit, are smaller still: per the commonly published tables, allowing no resplit at all costs roughly 0.06 percent compared with resplitting to four hands, per our piece on [resplit limits](https://21trainer.app/articles/resplit-limits-blackjack/).

**LS**, late surrender, lets you forfeit half the bet on a hopeless hand after the dealer checks for blackjack; it is worth about 0.08 percent to the player. **ES**, early surrender, is decided before the check, and the version offered against both a ten and an ace is worth roughly 0.6 percent, enough to erase most of a typical house edge, which is why you will almost never see it. Both rules and the hands they cover are in [early versus late surrender](https://21trainer.app/articles/early-vs-late-surrender/).

## The money: 3:2, 6:5, even money and insurance

**3:2** is the traditional natural payout: a blackjack on a 10 unit bet wins 15. **6:5** pays 12 on the same bet and raises the house edge by roughly 1.4 percentage points per the commonly published tables, several times the cost of any other rule on this page; the arithmetic is worked through in [3:2 versus 6:5](https://21trainer.app/articles/blackjack-3-2-vs-6-5/), and the rarer variants, 7:5 and outright 1:1, are toured in [every payout you will meet](https://21trainer.app/articles/blackjack-payout-variants/).

**Even money** is the offer, when you hold a blackjack against a dealer ace, to settle for a sure 1:1 win at once. It is insurance in disguise, and basic strategy declines it for the same reason it declines insurance. **Insurance** itself is a 2:1 side bet that the hole card is a ten value; the bet carries a house edge in the neighborhood of 7 percent, which is why [basic strategy says never take it](https://21trainer.app/articles/blackjack-insurance-explained/).

## The equipment: decks, penetration and the shufflers

**Deck count**, the number of decks in the shoe, appears on the rule card or placard. Other rules being equal, fewer decks are better for the player; going from one deck to eight costs roughly half a percentage point, a comparison that appears in our [payout article](https://21trainer.app/articles/blackjack-3-2-vs-6-5/) for scale against the 6:5 penalty.

**Penetration** is how deep into the shoe the dealer deals before the cut card ends the round, usually stated as a percentage of the shoe dealt. It is one of the numbers that matter most to counters: cutting off one deck or less is generally described as good in a six deck game, and two or more as poor. Our piece on [deck penetration](https://21trainer.app/articles/deck-penetration-explained/) explains the number and why it decides whether counting a table is worth attempting.

**Hand shuffle** means the dealer shuffles by hand. **ASM**, an automatic shuffling machine, shuffles a separate shoe off to the side between rounds and does not prevent counting by itself. **CSM**, a continuous shuffling machine, returns discards to the mix constantly, which keeps the composition near neutral and makes counting ineffective; the differences are laid out in [our CSM article](https://21trainer.app/articles/csm-continuous-shuffling-machines/).

## The chart codes: H, S, D, Ds, P, Ph and the rest

Strategy charts compress each cell into one or two letters, and the codes below are the main ones the 21 Trainer chart engine uses. If you have read [how to read a basic strategy chart](https://21trainer.app/articles/blackjack-basic-strategy-chart/), these are the letters inside its cells.

| Code | Meaning |
| --- | --- |
| H | Hit |
| S | Stand |
| D | Double if allowed, otherwise hit |
| Ds | Double if allowed, otherwise stand |
| P | Split |
| Ph | Split if double after split is allowed, otherwise hit |
| Pd | Split if double after split is allowed, otherwise double (hit if doubling is not allowed) |
| Ps | Split if double after split is allowed, otherwise stand |
| Rh | Surrender if allowed, otherwise hit |
| Rs | Surrender if allowed, otherwise stand |
| Rp | Surrender if allowed, otherwise split |

Two-letter codes that begin with P or R are conditional: they tell you both the best play and what to fall back to when the rule that enables it is missing. Ph on 2,2 against a 2 in a shoe game is the everyday example, a split when DAS is available and a hit otherwise. Which cells carry which codes shifts with the rules, the subject of our piece on [the hands that change with the rules](https://21trainer.app/articles/chart-changes-by-rule/); in 21 Trainer the codes are color coded and redraw whenever you change a setting, so the chart you drill always matches the rules you set.

## Frequently asked questions

### What does DAS mean on a blackjack table?

Double after split. It means that after you split a pair, the new hands may be doubled. Per the commonly published tables the rule is worth roughly 0.14 percentage points to the player, and it also changes strategy: several low pair splits, such as 2s and 3s against a dealer 2 or 3, are only worth making when doubling after the split is allowed.

### What is the difference between LS and ES in blackjack?

Both are surrender rules, where you forfeit half your bet and drop the hand. LS is late surrender, offered after the dealer has checked for blackjack, and it is worth about 0.08 percent to the player. ES is early surrender, decided before the check, which is why it is worth far more: the version offered against both a ten and an ace hands back roughly 0.6 percent, enough to erase most of a typical house edge, and it is accordingly rare.

### What does ENHC mean on a rule card?

European no hole card. The dealer takes no second card until the players have finished, so a dealer blackjack is revealed only after you have acted. Your doubles and splits can then lose both bets to a natural, which costs the player about 0.11 percentage points versus an American hole card game. Some rule cards describe the same condition as no peek: either way, the dealer does not check for blackjack before you act.

### What do the letters on a blackjack strategy chart mean?

H is hit and S is stand. D means double if allowed, otherwise hit, while Ds means double if allowed, otherwise stand. P is split, and Ph means split if double after split is allowed, otherwise hit. Rh means surrender if allowed, otherwise hit, and Rs means surrender if allowed, otherwise stand. The same code set drives the color coded charts in 21 Trainer, which redraw when you change the rules.

### Which rule card abbreviations matter most?

The payout line, before any abbreviation. A 6:5 blackjack payout costs roughly 1.4 percentage points against you, several times the cost of any other common rule on the card. After that, check the soft 17 rule, whether doubling after splits is allowed, and the surrender and doubling rules, which together move the edge by a few tenths of a point. Read the payout first and everything else second.

## Keep reading

- [What the Felt Actually Tells You Before You Sit](https://21trainer.app/articles/reading-the-blackjack-felt/)
- [The Handful of Hands That Change With the Rules](https://21trainer.app/articles/chart-changes-by-rule/)
- [How Rules Stack: Using a House Edge Calculator](https://21trainer.app/articles/house-edge-rule-calculator/)