[…] one of the chief occasions for setting up junctures […] is when one set of phonemes occurs at speech boundaries while its parallel set does not.
- Harris (1951), a pag.80

The simplest approach to setting up junctures is to watch […] for a set of phonemes which never occurs at the end (or at the beginning) of an utterance, while a parallel set of phonetically somewhat different phonemes occurs both there and within the utterance. E. g. in the sets of tentative phonemes /p‘, t‘, k‘/ and /p’, t’, k’/, the slightly aspirated /k‘/ which we hear in market never occurs in utterance final position, whereas the unreleased or released-but-not-aspirated /k’/ of 'What a lark!' Does occur there. This fact does not suffice to put these tentative phonemes together into one phoneme, because they contyrast in other positions: [aym'gowiŋ tu 'mark‘Əttu'dey.] ('I’m going to market today.') and [aym'gowiŋ tu'mark’Əttu'dey.] ('I’m going to mark it today.'). However, because the first set does not occur in the environment /—#/ (utterance final), we may decide to say that /k’/ plus /#/ substitutes for /k‘/, /p’/ + /#/ substitutes for /p‘/, etc. That is, the tentative /k’/ and /k‘/ are now members of one phoneme /k/, [k’] being the member which occurs before #. To get around the fact that both [k’] and [k‘] occur in some identical environments within utterances, as in the examples above, we then extend # so that it is not only a mark of utterance end but also a ‘zero’ phoneme which occurs after /k/, wherever that phoneme is represented by its member [k’] (whether within or at the end of utterances). Then 'I’m going to mark it today' becomes /aym'gowiŋtu'mark#Əttu'dey./, and 'lark' becomes /lark#/, while 'market' is /markƏt/. Now [k’] no longer contrasts with [k‘] anywhere, since there is always a /#/ after [k’]. Whenever we see /k#/, we know it represents the segmental element [k’], and when we hear the sound represented by [k’] we write it with the phonemic sequence /k#/. Furthermore, we will often find that the points at which junctures like /#/ are introduced within utterances are also points at which intermittently present pauses are occasionally made in pronouncing the utterance.
- Harris (1951), a pag.81