I am wanting to store some home made chilli sauce in jars (i've made
this sauce for about 20 years, but have always frozen it) despite many
hours of searching, I've been unable to find a guide of any sort on
how to achieve this (I want to use the type of lids that have the
safety button in the centre).

I know that the jars / lids i describe above create a vaccuum and that
the button in the lid is "sucked in", what i cant discover is how is
this achieved. Can anyone point me in the right direction ?.

All help gratefully received.