How does the virama mark change the sound of a Devanagari consonant?

In the Devanagari script, a consonant symbol by default represents the consonant followed by the inherent vowel a. The virama (also known as halant) is an angled substroke added to a consonant sign to indicate that the inherent vowel is removed.12

Essentially, the mark signals that the consonant stands alone as a pure consonant sound without any following vowel.21