[a] As with Skat and Bavarian Schafkopf there is a set of official rules, but numerous unofficial variants.

Before playing with a new group of players, it is advisable to agree on a specific set of rules before the first game.

[1] A 1783 novel describes the scene after a wedding dinner as the dining tables were cleared away and replaced by games tables: "here stood an Ombre table, there a noble Schafkopf was played, over there a game of forfeits, soon everybody was busy playing when suddenly the sound of the strings announced the arrival of the dance band..."[2] In 1796, we learn that students at Leipzig University liked to repair to disreputable bars to play Solo or Schafkopf for a couple of Dreiers.

[b] He hypothesises that the name comes from the practice of drawing the lines denoting points scored in the form of a stylised sheep's head.

Among Hammer's 9 variants were three played with a double pack that appear to be an early form of Doppelkopf.

These were all ace–ten games with the tens ranking low and were played by teams of two, in fixed partnerships, with bells as the trump suit.

They differed as follows:[6] Several post-war sources claim that Doppelkopf has its origins in a game called Wendish Schafkopf which, however, is first mentioned in the 1850s.

This may stem from a misreading of von Alvensleben by Georgens & Gagette-Georgens (1882) who stated that the original form of Schafkopf was Wendish, but then describes another different game: Hammer's type A.

In 1861, a short description was published of a game, probably referring to Types G and H above, that appeared under the alternative name of Marino (sic) as well as Schafkopf.

[9] The name Merino appears occasionally other contemporary sources, for example, an 1870 newspaper remarks: "It is strikingly clear how the common man recently viewed the world from the acquiescence of several playing card manufacturers who have designed the highest trump in German Solo, Obsern and Merino – the Ober of Acorns – with a face resembling that of Napoleon III.

"[10][d] In 1873 the name Doppelschaf(s)kopf appears for the first time in an Aichach newspaper which mentions a Doppelschafskopf Society (Doppelschafskopf-Gesellschaft).

"[18] In 1927, an early version of modern Doppelkopf is described by Robert Hülsemann who calls it an elaboration of the old German 3-4 player game of Schafkopf that, itself, has almost died out.

For the first time there were secret partnerships, the two players dealt the "Old Ones" (2 x ♣Q) joining forces against the other two, but were not allowed to announce their possession of these cards.

[20] The bonus for taking the last trick with the ♣J, Charlie Miller (Karlchen Müller), appears in Meister (1933) alongside another new feature, the sheep race (Hammelrennen), a contract in which everyone played for himself.

It bears traces of its origins, however, including the retention of Diamonds (the equivalent of Bells) as the trump suit.

Thus, each card exists twice in the pack (hence the name Doppelkopf), resulting in a total number of 240 points.

In tournament games, a stricter procedure is used to prevent players from gaining information about their opponents' hands.

In the normal game, the players who hold the queens of clubs (Die Alten = "the old women" or "the elders") or Obers of acorns constitute Re, while the other two are Kontra.

The special contracts, from lowest-ranking to highest-ranking, are: The 10 of hearts (often called the Dulle or Tolle) is the highest trump in every normal game as well as any suit solo.

One noteworthy result of this rule is that there are only six non-trump cards left in hearts, making this suit more likely to be trumped in the first trick it is played.

The kinds of solo games are, according to the official rules: During play, a player may make announcements claiming that their team will succeed in achieving a specific goal.

Apart from increasing the game value, the bids fulfill the role of clarifying which side the player who makes them belongs to.

The negative announcements (an Absage is a rejection) are those claiming that the opposition are not going to achieve certain scores e.g. "No 90" (keine 90) or "Schwarz" i.e. "no tricks".

It is recommended to avoid leading the second round of hearts, because of the danger of giving a ruff and discard to the opponents, since there are only six cards in the suit.

Announcing Re or Kontra earlier than when one needs to, for example, on the first play rather than the second, indicates possession of additional strength (similar conceptually to jump bidding in Contract Bridge).

A compulsory solo, particularly towards the end, should almost always have Kontra said if the declarer does not say Re to increase the game value when the soloist loses.

That means, that these cards become the highest trumps in play, outranking the Dullen (tens of hearts) and Alten (queens of clubs).

Other variants include the announcement at any point during the game, often breaking the opposing team's bid or the possibility of 'super piglets', if one holds both nines of diamonds.

In some variants, only the first played fox becomes a piglet at the top of the trump suit while the second one still ranks low.

That means, those nines of diamonds become the highest trumps in play, outranking the piglets, the Dullen and Alten.