Consonant clusters are formed by putting two signs or more ( up to 5 ) closely together, forming a ligature. When consonants occur in clusters, special conjunct letters are used.
In principle, clusters or ligatures may be formed by randomly combining consonants, a process called samyoga (meaning "yoked together"). Many ligatures can be formed theoretically, some ligatures are just used for transcribing foreign words or are obsolete and not in common use.
In practice, approximately a thousand conjuncts exists, most of which have two or three consonants in them. There are some with four and at least one well known conjunct with five consonants. Theoretically to all of these conjuncts or ligatures, one of the 14 vowels and diacritical marks can be added.
Identifying conjuncts in written texts is important. The use of the "half form" of a consonant in a cluster is a practice allowed for many conjuncts particularly those which include a vertical stroke in their signs. Though many of the half forms are not clearly defined in a system, many special shapes were formed for the conjuncts.
In most cases the consonants were written one below the other vertically, but reduced in size, building a new stack. The significant problem of a calligraphed ligature with more then two consonants is the vertical height. The ligature should be calligraphed in the same height as a normal basic consonant. All line spacings in a document should be of equal height. A conjunct with more consonants will crash into the ligature of the line below. The individual consonants thus had to be reduced in size to such an extent that in some cases their identification became a problem. So as, not to increase the vertical height of the conjunct both systems are used in combination: The half form and the one below the other form together. It is not unusual to find different representations for the same conjunct, or the conjuncts create new shapes of special signs. The range of possibilities is quite wide- and various of strategies of merging consonants to clusters are employed.