@final consonant crushing

In practice, a Sanskrit word (/pada) can only end in a vowel, or in one of these nine consonants —

m म् s स् n न् d द् r र् g ग् D ड् b ब् G ङ्.

When some grammar rule places any other consonant at word-end, it is "forbidden", and must be "crushed" into one of the "allowed" consonants m म् s स् n न् d द् r र् g ग् D ड् b ब् G ङ्, according to the table below.

After that, the consonant will suffer the usual changes of padafinal consonants. I have added at the right side of the table a column showing the changes before pause.

replace padafinal	with	before pause	see examples at
h	d or D or g	t or T or k	crushing of h
z j	D or g	T or k	crushing of z j
k kh g gh c	g	k	crushing of ku c
T Th D Dh ch jh S	D	T	crushing of Tu ch jh S
t th d dh	d	t	crushing of tu
p ph b bh	b	p	crushing of pu
s r	no change	H
n m G	no change
y l v J N	do not occur

Now this is tricky —

The way /pANini explains things, all t and all d ALWAYS turn into d at the end of a /pada, regardless of what comes later —

suhRd + su → suhRd

vidyut + su → vidyut → vidyud by jhalAJjazonte

Then the d will maybe change into something else, depending on what comes later. As for instance, it will turn into t before k —

suhRd + kutra → suhRt kutra

vidyud + kutra → vidyut kutra

it will stay d before a vowel or a g —

suhRd + atra → suhRd atra

vidyud + atra → vidyud atra

and will turn into t before pause —

suhRd + pause → suhRt

vidyud + pause → vidyut

The views of the Western grammarians are slightly different. According to them, d changes into t whenever it is at the end of a /pada, then that t turns into d before a vowel or a g , and stays t before k and pause. That's a different way of explaining but you get the same suhRt kutra , vidyut kutra , suhRd atra ... as above.

Because I have read both the Western grammarians and /pANini, I got somehow confused and I will say sometimes that suhRd changes into suhRt and other times I will say that suhRt changes into suhRd. Do not worry much about that; you just have remember that d and t are exactly the same thing when they are padafinal.